[{"data":1,"prerenderedAt":2234},["ShallowReactive",2],{"i-kinnu:logo":3,"i-kinnu:origami-folding":8,"pathway-science-physics":12,"i-lucide:chevron-right":2229,"i-lucide:tag":2232},{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":7},0,27,false,"\u003Cg fill=\"none\">\u003Cpath d=\"M0.046875 1.05555C0.046875 1.03541 0.048197 1.01579 0.0507438 0.996728C0.0987149 0.438619 0.586845 0 1.18194 0H25.4398C26.451 0 26.9575 1.171 26.2424 1.85585L15.7301 11.9243L1.31574 0.903476C1.17475 0.79568 1.01137 0.761884 0.859586 0.784111L26.2936 25.1441C27.0086 25.829 26.5022 27 25.4909 27H1.18194C0.555061 27 0.046875 26.5133 0.046875 25.9129V1.05555Z\" fill=\"currentColor\"/>\u003C/g>",{"left":4,"top":4,"width":9,"height":10,"rotate":4,"vFlip":6,"hFlip":6,"body":11},1000,236,"\u003Cg fill=\"none\">\u003Cpath fill-rule=\"evenodd\" clip-rule=\"evenodd\"\n    d=\"M193.68 38.2238C195.994 38.2238 197.87 40.0989 197.87 42.412V231.812C197.87 234.125 195.994 236 193.68 236H4.19013C1.87603 236 2.02305e-07 234.125 0 231.812V42.412C-2.02305e-07 40.0989 1.87603 38.2238 4.19013 38.2238H193.68ZM111.76 89.0072C111.685 87.9474 110.572 87.2905 109.608 87.7376L96.8872 93.641C95.7786 94.1554 95.702 95.7016 96.7545 96.3225L101.579 99.167C94.7045 109.365 90.5733 122.892 90.5732 137.642C90.5733 154.323 95.8569 169.439 104.416 179.945C105.301 181.032 106.9 181.196 107.987 180.311C109.075 179.426 109.238 177.828 108.353 176.741C100.621 167.25 95.6522 153.305 95.6521 137.642C95.6522 123.661 99.6138 111.051 105.963 101.754L110.456 104.403C111.508 105.024 112.826 104.21 112.74 102.991L111.76 89.0072ZM9.63194 136.286C9.14864 136.286 8.75684 136.678 8.75684 137.161C8.7569 137.644 9.14868 138.035 9.63194 138.035H17.2161C17.6993 138.035 18.0912 137.644 18.0912 137.161C18.0912 136.678 17.6994 136.286 17.2161 136.286H9.63194ZM22.6813 136.286C22.198 136.286 21.8062 136.678 21.8062 137.161C21.8063 137.644 22.1981 138.035 22.6813 138.035H30.2655C30.7487 138.035 31.1406 137.644 31.1406 137.161C31.1406 136.678 30.7488 136.286 30.2655 136.286H22.6813ZM35.7464 136.286C35.2631 136.286 34.8713 136.678 34.8713 137.161C34.8713 137.644 35.2631 138.035 35.7464 138.035H44.4973C44.9805 138.035 45.3724 137.644 45.3724 137.161C45.3724 136.678 44.9806 136.286 44.4973 136.286H35.7464ZM49.9977 136.286C49.5144 136.286 49.1226 136.678 49.1226 137.161C49.1226 137.644 49.5144 138.035 49.9977 138.035H57.5819C58.0651 138.035 58.4569 137.644 58.457 137.161C58.457 136.678 58.0651 136.286 57.5819 136.286H49.9977ZM63.0783 136.286C62.595 136.286 62.2032 136.678 62.2032 137.161C62.2033 137.644 62.5951 138.035 63.0783 138.035H70.6625C71.1457 138.035 71.5375 137.644 71.5376 137.161C71.5376 136.678 71.1457 136.286 70.6625 136.286H63.0783ZM76.1277 136.286C75.6444 136.286 75.2526 136.678 75.2526 137.161C75.2527 137.644 75.6445 138.035 76.1277 138.035H83.7119C84.1951 138.035 84.5869 137.644 84.587 137.161C84.587 136.678 84.1951 136.286 83.7119 136.286H76.1277ZM102.266 136.286C101.782 136.286 101.39 136.678 101.39 137.161C101.391 137.644 101.782 138.035 102.266 138.035H109.85C110.333 138.035 110.725 137.644 110.725 137.161C110.725 136.678 110.333 136.286 109.85 136.286H102.266ZM115.338 136.286C114.855 136.286 114.463 136.678 114.463 137.161C114.463 137.644 114.855 138.035 115.338 138.035H122.923C123.406 138.035 123.798 137.644 123.798 137.161C123.798 136.678 123.406 136.286 122.923 136.286H115.338ZM128.403 136.286C127.92 136.286 127.528 136.678 127.528 137.161C127.528 137.644 127.92 138.035 128.403 138.035H135.988C136.471 138.035 136.863 137.644 136.863 137.161C136.863 136.678 136.471 136.286 135.988 136.286H128.403ZM141.468 136.286C140.985 136.286 140.593 136.678 140.593 137.161C140.593 137.644 140.985 138.035 141.468 138.035H149.053C149.536 138.035 149.928 137.644 149.928 137.161C149.928 136.678 149.536 136.286 149.053 136.286H141.468ZM154.541 136.286C154.058 136.286 153.666 136.678 153.666 137.161C153.666 137.644 154.058 138.035 154.541 138.035H162.125C162.609 138.035 163 137.644 163.001 137.161C163.001 136.678 162.609 136.286 162.125 136.286H154.541ZM167.614 136.286C167.131 136.286 166.739 136.678 166.739 137.161C166.739 137.644 167.131 138.035 167.614 138.035H175.198C175.681 138.035 176.073 137.644 176.073 137.161C176.073 136.678 175.681 136.286 175.198 136.286H167.614ZM180.671 136.286C180.188 136.286 179.796 136.678 179.796 137.161C179.796 137.644 180.188 138.035 180.671 138.035H188.255C188.739 138.035 189.13 137.644 189.131 137.161C189.131 136.678 188.739 136.286 188.255 136.286H180.671Z\"\n    fill=\"currentColor\" />\n  \u003Cpath fill-rule=\"evenodd\" clip-rule=\"evenodd\"\n    d=\"M444.85 38.2277C447.164 38.2277 449.04 40.1028 449.04 42.4159V132.928C449.04 135.241 447.164 137.116 444.85 137.116H255.36C253.046 137.116 251.17 135.241 251.17 132.928V42.4159C251.17 40.1028 253.046 38.2277 255.36 38.2277H444.85ZM361.96 125.388C361.618 125.046 361.064 125.046 360.722 125.388L354.534 131.572C354.192 131.914 354.192 132.468 354.534 132.81C354.876 133.151 355.43 133.151 355.772 132.81L361.96 126.624C362.301 126.283 362.301 125.73 361.96 125.388ZM371.047 116.311C370.705 115.969 370.15 115.969 369.809 116.311L364.446 121.671C364.104 122.012 364.104 122.567 364.446 122.908C364.788 123.249 365.342 123.25 365.684 122.908L371.047 117.548C371.388 117.207 371.388 116.652 371.047 116.311ZM380.124 107.246C379.782 106.904 379.227 106.904 378.885 107.246L373.523 112.606C373.181 112.948 373.181 113.502 373.523 113.844C373.864 114.185 374.419 114.185 374.761 113.844L380.124 108.483C380.465 108.142 380.465 107.587 380.124 107.246ZM385.736 65.8841C385.891 64.6727 384.622 63.7845 383.536 64.3434L371.069 70.7636C370.124 71.2504 369.96 72.5334 370.752 73.2424L381.2 82.5938C382.11 83.4081 383.561 82.8672 383.717 81.6557L384.393 76.3725C391.143 77.1933 398.567 80.7709 404.771 86.9711C411.124 93.3213 414.726 100.952 415.43 107.827C415.573 109.221 416.819 110.236 418.214 110.093C419.609 109.95 420.624 108.703 420.481 107.309C419.644 99.1317 415.435 90.4514 408.362 83.3817C401.466 76.489 393.038 72.3185 385.038 71.338L385.736 65.8841ZM389.2 98.1733C388.859 97.8319 388.304 97.8318 387.962 98.1733L382.6 103.534C382.258 103.875 382.258 104.429 382.6 104.771C382.941 105.112 383.496 105.112 383.838 104.771L389.2 99.4108C389.542 99.0693 389.542 98.5149 389.2 98.1733ZM398.262 89.1047C397.92 88.7633 397.365 88.7632 397.024 89.1047L391.661 94.4649C391.319 94.8065 391.319 95.3608 391.661 95.7024C392.002 96.0436 392.557 96.0438 392.899 95.7024L398.262 90.3421C398.603 90.0007 398.603 89.4463 398.262 89.1047ZM416.431 70.9616C416.089 70.6202 415.534 70.6201 415.193 70.9616L409.83 76.3218C409.488 76.6634 409.488 77.2177 409.83 77.5592C410.172 77.9005 410.726 77.9007 411.068 77.5592L416.431 72.199C416.772 71.8575 416.772 71.3032 416.431 70.9616ZM425.508 61.891C425.166 61.5496 424.611 61.5495 424.27 61.891L418.907 67.2512C418.565 67.5928 418.565 68.1471 418.907 68.4887C419.249 68.8299 419.803 68.8301 420.145 68.4887L425.508 63.1284C425.849 62.787 425.849 62.2326 425.508 61.891ZM434.569 52.8146C434.227 52.4731 433.673 52.4731 433.331 52.8146L427.968 58.1748C427.626 58.5163 427.627 59.0706 427.968 59.4122C428.31 59.7534 428.864 59.7537 429.206 59.4122L434.569 54.052C434.91 53.7105 434.91 53.1562 434.569 52.8146ZM443.638 43.7479C443.296 43.4065 442.742 43.4064 442.4 43.7479L437.037 49.1081C436.695 49.4496 436.696 50.004 437.037 50.3455C437.379 50.6868 437.933 50.687 438.275 50.3455L443.638 44.9853C443.98 44.6438 443.979 44.0895 443.638 43.7479Z\"\n    fill=\"currentColor\" />\n  \u003Cpath fill-rule=\"evenodd\" clip-rule=\"evenodd\"\n    d=\"M684.066 38.2277C687.798 38.2281 689.667 42.7391 687.027 45.3773L596.473 135.889C595.687 136.675 594.621 137.116 593.51 137.116H506.335C504.021 137.116 502.145 135.241 502.145 132.928V42.4159C502.145 40.1028 504.021 38.2277 506.335 38.2277H684.066ZM514.603 124.566C514.261 124.224 513.707 124.224 513.365 124.566L507.178 130.751C506.836 131.093 506.836 131.646 507.178 131.988C507.519 132.329 508.073 132.329 508.415 131.988L514.603 125.803C514.945 125.462 514.945 124.908 514.603 124.566ZM523.689 115.491C523.348 115.15 522.794 115.15 522.452 115.491L517.09 120.852C516.748 121.193 516.748 121.747 517.09 122.088C517.431 122.43 517.985 122.43 518.327 122.088L523.689 116.728C524.031 116.386 524.031 115.833 523.689 115.491ZM532.102 65.8295C530.707 65.6872 529.46 66.7017 529.318 68.0957C529.175 69.4896 530.189 70.7355 531.584 70.8787C538.463 71.5825 546.096 75.1826 552.45 81.5329C558.723 87.8037 562.312 95.3226 563.079 102.13L557.738 102.392C556.518 102.452 555.865 103.855 556.607 104.827L565.115 115.969C565.76 116.814 567.051 116.751 567.611 115.847L574.992 103.928C575.635 102.889 574.848 101.555 573.628 101.615L568.161 101.882C568.161 101.878 568.162 101.874 568.161 101.871C567.324 93.6931 563.114 85.0124 556.041 77.9425C548.968 70.873 540.283 66.6668 532.102 65.8295ZM532.766 106.421C532.425 106.079 531.871 106.079 531.529 106.421L526.166 111.781C525.825 112.123 525.825 112.676 526.166 113.018C526.508 113.359 527.062 113.359 527.403 113.018L532.766 107.657C533.108 107.316 533.108 106.762 532.766 106.421ZM541.843 97.3445C541.501 97.003 540.948 97.003 540.606 97.3445L535.243 102.705C534.901 103.046 534.902 103.6 535.243 103.941C535.585 104.283 536.139 104.283 536.48 103.941L541.843 98.5809C542.185 98.2393 542.185 97.686 541.843 97.3445ZM550.92 88.2778C550.578 87.9363 550.025 87.9363 549.683 88.2778L544.32 93.638C543.978 93.9796 543.978 94.5329 544.32 94.8745C544.662 95.2161 545.215 95.2161 545.557 94.8745L550.92 89.5142C551.262 89.1727 551.262 88.6193 550.92 88.2778ZM569.066 70.1405C568.724 69.799 568.17 69.7991 567.829 70.1405L562.466 75.5008C562.124 75.8423 562.124 76.3956 562.466 76.7372C562.808 77.0788 563.361 77.0788 563.703 76.7372L569.066 71.377C569.407 71.0354 569.407 70.4821 569.066 70.1405ZM578.143 61.0699C577.801 60.7284 577.247 60.7285 576.906 61.0699L571.543 66.4302C571.201 66.7717 571.201 67.3251 571.543 67.6666C571.885 68.0082 572.438 68.0082 572.78 67.6666L578.143 62.3064C578.484 61.9648 578.484 61.4115 578.143 61.0699ZM587.219 51.9896C586.878 51.6481 586.324 51.6481 585.982 51.9896L580.62 57.3498C580.278 57.6914 580.278 58.2447 580.62 58.5863C580.961 58.9279 581.515 58.9279 581.857 58.5863L587.219 53.2261C587.561 52.8845 587.561 52.3312 587.219 51.9896ZM596.288 42.9249C595.947 42.5833 595.392 42.5833 595.05 42.9249L589.689 48.2851C589.347 48.6267 589.347 49.18 589.689 49.5216C590.03 49.863 590.584 49.8631 590.926 49.5216L596.288 44.1613C596.63 43.8198 596.63 43.2664 596.288 42.9249Z\"\n    fill=\"currentColor\" />\n  \u003Cpath fill-rule=\"evenodd\" clip-rule=\"evenodd\"\n    d=\"M850.814 38.2277C854.547 38.2281 856.416 42.739 853.777 45.3773L763.223 135.889C762.437 136.674 761.371 137.116 760.26 137.116H673.176C669.443 137.116 667.574 132.605 670.213 129.966L760.768 39.4544C761.554 38.6692 762.62 38.2277 763.731 38.2277H850.814ZM761.338 121.8C760.855 121.8 760.463 122.191 760.463 122.674V131.13H762.213V122.674C762.213 122.191 761.821 121.8 761.338 121.8ZM761.338 108.971C760.855 108.971 760.463 109.363 760.463 109.846V118.301H762.213V109.846C762.213 109.363 761.821 108.971 761.338 108.971ZM761.338 96.1402C760.855 96.1406 760.463 96.5321 760.463 97.0149V105.47H762.213V97.0149C762.213 96.532 761.821 96.1404 761.338 96.1402ZM782.263 71.887C781.043 71.951 780.395 73.3571 781.139 74.3257L784.474 78.6631C779.115 82.951 771.242 85.7443 762.35 85.7444C753.366 85.7442 745.421 82.8944 740.059 78.5305C738.972 77.6461 737.373 77.8099 736.488 78.8961C735.602 79.983 735.766 81.582 736.853 82.467C743.231 87.6574 752.348 90.8207 762.35 90.8209C772.209 90.8208 781.205 87.746 787.568 82.6884L790.833 86.9341C791.577 87.9025 793.103 87.6391 793.479 86.4767L797.791 73.138C798.118 72.127 797.33 71.1017 796.268 71.1566L782.263 71.887ZM761.338 70.4847C760.855 70.4851 760.463 70.8767 760.463 71.3594V79.8147H762.213V71.3594C762.213 70.8766 761.821 70.485 761.338 70.4847ZM761.338 57.656C760.855 57.6564 760.463 58.048 760.463 58.5307V66.986H762.213V58.5307C762.213 58.0479 761.821 57.6563 761.338 57.656ZM761.338 44.8293C760.855 44.8297 760.463 45.2212 760.463 45.704V54.1592H762.213V45.704C762.213 45.2211 761.821 44.8295 761.338 44.8293Z\"\n    fill=\"currentColor\" />\n  \u003Cpath\n    d=\"M995.759 38.2277C999.53 38.228 1001.42 42.5171 998.752 45.0253L959.55 81.9005L905.796 41.5363C905.271 41.1418 904.662 41.0182 904.096 41.0994L997.485 130.319C1000.15 132.828 998.262 137.116 994.491 137.116H905.298C902.96 137.116 901.065 135.333 901.065 133.134V42.0941C901.065 42.0204 901.07 41.9483 901.079 41.8786C901.258 39.8345 903.079 38.2277 905.298 38.2277H995.759Z\"\n    fill=\"currentColor\" />\n  \u003Cpath\n    d=\"M505.873 0C506.657 4.57042e-05 507.307 0.195499 507.823 0.587023C508.338 0.969046 508.596 1.53802 508.596 2.29251C508.596 2.76034 508.467 3.19015 508.209 3.58162C507.951 3.96344 507.497 4.26401 506.848 4.48361V4.54114C507.65 4.67487 508.205 4.96191 508.51 5.4012C508.816 5.83087 508.969 6.31772 508.969 6.86193C508.969 7.74056 508.672 8.41851 508.08 8.89604C507.497 9.38304 506.733 9.62731 505.787 9.62738C504.861 9.62738 504.158 9.42172 503.68 9.0111C503.212 8.60054 502.935 8.08005 502.849 7.44993L503.881 7.10571L503.924 7.24028C504.035 7.54934 504.211 7.82925 504.454 8.07986C504.731 8.36635 505.166 8.50986 505.758 8.50989C506.465 8.50989 506.943 8.32772 507.191 7.9648C507.449 7.6019 507.579 7.20078 507.579 6.7615C507.579 6.2173 507.378 5.80683 506.977 5.52992C506.585 5.25295 505.93 5.10026 505.013 5.07161V4.15402C505.901 4.12537 506.489 3.92484 506.776 3.55237C507.062 3.18009 507.206 2.82242 507.206 2.47876C507.206 1.62801 506.752 1.17539 505.845 1.12237L505.658 1.11749C505.467 1.11752 505.242 1.14605 504.985 1.2033C504.736 1.25105 504.511 1.3274 504.31 1.43245L504.081 2.56457L503.05 2.44951L503.322 0.687461C503.666 0.49653 504.068 0.33454 504.526 0.200875C504.985 0.0671945 505.434 0 505.873 0Z\"\n    fill=\"currentColor\" />\n  \u003Cpath\n    d=\"M905.727 2.30616L904.638 2.4066L904.466 1.26083H901.428V3.72497C901.533 3.71544 901.643 3.71034 901.757 3.71034H902.086C902.755 3.71034 903.386 3.78668 903.979 3.93949C904.58 4.09229 905.068 4.38363 905.44 4.8132C905.822 5.23335 906.014 5.84949 906.014 6.66106C906.014 7.64468 905.722 8.38068 905.14 8.86776C904.557 9.36434 903.783 9.6127 902.818 9.61275C901.91 9.61275 901.213 9.40711 900.725 8.99648C900.248 8.59544 899.96 8.08007 899.865 7.44993L900.911 7.10571C901.007 7.49723 901.203 7.8271 901.499 8.09449C901.795 8.37131 902.211 8.50985 902.746 8.50989C903.395 8.50989 903.869 8.33787 904.165 7.99405C904.461 7.65981 904.609 7.22507 904.609 6.69031C904.609 5.87861 904.337 5.3625 903.792 5.14279C903.248 4.91361 902.612 4.79958 901.886 4.79955C901.695 4.79955 901.489 4.80365 901.27 4.8132C901.059 4.82275 900.854 4.83701 900.653 4.85611L900.224 4.44071V0.143343H905.569L905.727 2.30616Z\"\n    fill=\"currentColor\" />\n  \u003Cpath fill-rule=\"evenodd\" clip-rule=\"evenodd\"\n    d=\"M765.49 6.04576H766.966L766.837 7.14862H765.49V9.48404H764.185V7.14862H759.857L759.713 6.04576L762.909 0.143343H765.49V6.04576ZM760.96 6.04576H764.185V1.26083H763.541L760.96 6.04576Z\"\n    fill=\"currentColor\" />\n  \u003Cpath d=\"M4.80573 6.47481H6.41154V7.60693H1.81068V6.47481H3.50235V1.27546H1.81068V0.143343H4.80573V6.47481Z\"\n    fill=\"currentColor\" />\n  \u003Cpath\n    d=\"M254.359 0C255.353 0 256.055 0.239186 256.466 0.716715C256.877 1.18447 257.083 1.68072 257.083 2.20573C257.083 2.85516 256.849 3.44346 256.38 3.96875C255.912 4.49397 255.348 4.96638 254.689 5.38657C254.039 5.79717 253.437 6.15968 252.883 6.47481H256.423L256.538 5.42948L257.599 5.51529L257.426 7.60693H251.407L251.292 6.58987C252.582 5.73032 253.638 4.98523 254.46 4.35489C255.281 3.71509 255.693 3.05632 255.693 2.37832C255.693 1.53787 255.166 1.11749 254.115 1.12237L254.115 1.11749C253.924 1.11754 253.695 1.14604 253.427 1.2033C253.16 1.25104 252.916 1.32238 252.697 1.41783L252.467 2.47876L251.45 2.3637L251.707 0.60165C252.118 0.401088 252.563 0.253475 253.041 0.15797C253.519 0.0529708 253.958 1.99446e-05 254.359 0Z\"\n    fill=\"currentColor\" />\u003C/g>",{"id":13,"data":14,"type":15,"maxContentLevel":27,"version":28,"tiles":29},"98f8c278-78d5-4651-9276-9afbff3c9cba",{"type":15,"title":16,"tagline":17,"description":17,"featureImageSquare":18,"baseColor":19,"emoji":20,"shapePreference":21,"allowContentSuspension":22,"allowContentEdits":22,"editorsChoice":6,"accreditations":23,"certificatePriceLevel":21,"certificationTitle":26},8,"Physics","Discover the laws and principles that govern our entire universe","6f7be1a8-2c67-4390-832d-16942b19c665","#72A795","💥",2,true,[24],{"authority":25},1,"Core Concepts in Physics",9,3,[30,237,419,612,804,991,1164,1349,1533,1728,1889,2031],{"id":31,"data":32,"type":27,"maxContentLevel":28,"version":21,"orbs":35},"7a9fd8fc-766d-4f10-a976-b0867ce7d7ea",{"type":27,"title":33,"tagline":34},"Introduction to Motion","The many kinds of force that keep things moving.",[36,92,153],{"id":37,"data":38,"type":21,"version":21,"maxContentLevel":28,"pages":40},"4d6a27f6-6d91-4a90-b19c-005b3a10f700",{"type":21,"title":39},"Introduction to Physics",[41,57,75],{"id":42,"data":43,"type":25,"maxContentLevel":28,"version":21,"reviews":47},"e9394bb5-abf8-4e82-b88d-305f6b25e597",{"type":25,"title":44,"markdownContent":45,"audioMediaId":46},"What is physics, and why does it matter?","Physics is the study of matter, energy, and their interactions. It is a fundamental science that underpins all other sciences and technologies. Physics has been essential to human progress since ancient times: without an understanding of physics we could not have built the pyramids in Egypt, for example. Today, physics plays an important role in our everyday lives: from medical imaging techniques such as X-rays and MRI scans to household appliances like refrigerators and washing machines.\n\nThe importance of physics goes beyond practical applications; it helps us understand how the universe works at its most basic level. By studying motion, forces, energy transfer, electricity and magnetism we can gain insight into phenomena ranging from planetary orbits to quantum mechanics. This knowledge allows us to make predictions about natural events with remarkable accuracy - for instance predicting eclipses centuries in advance or sending spacecrafts millions of miles away with pinpoint precision.","767affd6-c58b-4ac6-bbe1-7b53219a2079",[48],{"id":49,"data":50,"type":51,"version":25,"maxContentLevel":28},"b3b7ce80-fe38-4cb9-a17b-16bed58d29c0",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":52,"binaryCorrect":54,"binaryIncorrect":55},11,[53],"What is the fundamental science that underpins all other sciences and technologies?",[16],[56],"Chemistry",{"id":58,"data":59,"type":25,"maxContentLevel":28,"version":21,"reviews":63},"60219d22-9769-4e35-be12-d0ff31c082b2",{"type":25,"title":60,"markdownContent":61,"audioMediaId":62},"A very brief history of physics","The history of physics is long and fascinating, stretching back to ancient times. Ancient philosophers such as Aristotle and Plato were among the first to explore the nature of motion, laying down some of the earliest foundations for what would become classical physics.\n\nThis was further developed by scientists like Galileo Galilei in the 16th century who, according to legend, dropped spheres from the Leaning Tower of Pisa to demonstrate that (air resistance excluded) all objects fall at the same acceleration regardless of their mass.\n\n![Graph](image://f88d7735-151a-4322-a55a-cb04ba828f9d \" James Clerk Maxwell\")\n\nIn 1687 Isaac Newton published his famous work 'Philosophiae Naturalis Principia Mathematica', which laid out three laws of motion that are still taught today. It also introduced Newton's law of universal gravitation, which explained how gravity works on an astronomical scale - from planets orbiting stars to comets travelling through space.\n\nLater, in the 19th century, James Clerk Maxwell unified electricity and magnetism into a single theory known as electromagnetism. In the early 20th century, Albert Einstein revolutionised our understanding of the universe with his theories on relativity. Together these discoveries have shaped modern physics and enabled us to understand phenomena ranging from black holes to quantum mechanics.","d041d442-1a20-4d9b-aacf-1a65c1d58576",[64],{"id":65,"data":66,"type":51,"version":25,"maxContentLevel":28},"e50ae8e9-f8ff-48c4-b1b3-492b97c35aee",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":67,"multiChoiceCorrect":69,"multiChoiceIncorrect":71},[68],"Who famously dropped spheres from the Leaning Tower of Pisa to demonstrate that all objects fall at the same rate regardless of their mass?",[70],"Galileo Galilei",[72,73,74],"Isaac Newton","James Clerk Maxwell","Albert Einstein",{"id":76,"data":77,"type":25,"maxContentLevel":28,"version":21,"reviews":81},"f6a0edf3-5b53-47d2-87ad-bf236a4f70fe",{"type":25,"title":78,"markdownContent":79,"audioMediaId":80},"The scientific method","![Graph](image://dbe533c8-5940-4895-b43d-1cd0c02c7704 \"Isaac Newton under a tree\")\n\nThe scientific method is a powerful tool used by physicists to explain the natural world. It involves forming hypotheses based on observations and induction, then testing them through experiment. This process of trial and error allows us to gain insight into how things work at their most basic level.\n\nFor example, when Isaac Newton observed an apple falling from a tree he formed the hypothesis that, in a vacuum, all objects fall at the same acceleration regardless of their mass - this was later tested in experiments such as the Cavendish experiments, the results of which further supported Newton's hypothesis.\n\nIt is important to remember that being wrong can be just as valuable as being right: without disproving false theories we would never know what is true! The concept of the null hypothesis - where one assumes something is not true until proven otherwise - has been essential in helping scientists make progress over centuries. By challenging existing beliefs we are able to uncover new truths about our universe and further our understanding of physics.","8b983594-7d6c-4986-857b-17b5b145e1c4",[82],{"id":83,"data":84,"type":51,"version":25,"maxContentLevel":28},"ca3b3faf-003a-4ec2-a3e9-05bdc6c897d9",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":85,"multiChoiceCorrect":87,"multiChoiceIncorrect":89},[86],"What is the concept of assuming something is not true until proven otherwise known as?",[88],"The null hypothesis",[78,90,91],"Induction","The Cavendish experiment",{"id":93,"data":94,"type":21,"version":25,"maxContentLevel":28,"pages":96},"45966a74-9e90-464c-a29b-51795958f347",{"type":21,"title":95},"Fundamentals of Motion",[97,122,137],{"id":98,"data":99,"type":25,"maxContentLevel":28,"version":25,"reviews":103},"1b35612d-7d8e-4273-9afe-5c38db04ad35",{"type":25,"title":100,"markdownContent":101,"audioMediaId":102},"What is motion?","Motion is the act of changing position or direction over time. It can be described in terms of a change in an object's location or velocity. There are four main types of motion: linear, oscillating, rotary and reciprocating.\n\n ![Graph](image://d10df36f-7938-4fe8-88cc-ca400beb44de \"A ferris wheel exhibits rotary motion\")\n\nLinear motion is when an object moves in a straight line; examples include cars on highways or objects falling to earth. Oscillating motion occurs when an object moves back and forth about a central point; this could be seen in pendulums swinging from side to side. \n\nRotary motion involves objects spinning around their own axis like wheels turning on a car axle or planets rotating around their axis. Finally, reciprocating motion describes objects moving repetitively back-and-forth along the same path like pistons inside engines or pumps pushing water through pipes.\n\nFrom tiny nanomachines used in medical treatments to massive turbines generating electricity - understanding how each type of motion works helps us make use of them efficiently for our benefit.\n\n","d24a2bcb-1384-4b3e-8077-2da4952cfc61",[104,114],{"id":105,"data":106,"type":51,"version":25,"maxContentLevel":28},"9ce1793c-4358-4724-94e0-2015288b182d",{"type":51,"reviewType":25,"spacingBehaviour":25,"activeRecallQuestion":107,"activeRecallAnswers":109},[108],"What are the four main types of motion?",[110,111,112,113],"Linear","Oscillating","Rotary","Reciprocating",{"id":115,"data":116,"type":51,"version":25,"maxContentLevel":28},"c423060a-b622-4a3c-9000-7d9afab05e2c",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":117,"multiChoiceCorrect":119,"multiChoiceIncorrect":121},[118],"Which of these is NOT one of the four main types of motion?",[120],"Lateral",[110,111,112],{"id":123,"data":124,"type":25,"maxContentLevel":28,"version":25,"reviews":128},"acdd04b8-f33b-4894-9f2d-98a39f0b73b2",{"type":25,"title":125,"markdownContent":126,"audioMediaId":127},"Distance and Displacement","Distance and displacement are two important concepts in physics. Distance is the total length of a path travelled, while displacement is the difference between an object's initial position and its final position. To illustrate this concept, imagine a person walking around a circular track. If this track is five miles long, they will have covered a distance of five miles as they walk around it. But when they complete the loop, their displacement remains zero since they end up at the same point where they started.\n\n ![Graph](image://97707bb3-fec6-4cda-ab17-06a2bb770d49 \"A circular track with a person walking around it\")\n\nThe concepts of distance and displacement don’t just apply to people walking on tracks or roads. They are also a useful way to describe motion throughout the universe. We can observe similar phenomena in motion within nature such as water molecules moving through rivers or air particles travelling through wind currents - all of which demonstrate how distance does not always equal displacement.\n\n","506b63a1-837f-4c7d-b21a-621c01bd31e2",[129],{"id":130,"data":131,"type":51,"version":25,"maxContentLevel":28},"42a61c83-18ea-4f57-b2b6-1bc2d57e0d41",{"type":51,"reviewType":132,"spacingBehaviour":25,"clozeQuestion":133,"clozeWords":135},4,[134],"Distance is the total length of a path travelled, while displacement is the difference between an object's initial and final position.",[136],"displacement",{"id":138,"data":139,"type":25,"maxContentLevel":28,"version":25,"reviews":143},"83ad1da9-a476-465c-939e-ddb7ca50dd39",{"type":25,"title":140,"markdownContent":141,"audioMediaId":142},"Speed and velocity","Speed and velocity are two related concepts in physics, but they have distinct meanings. Speed is a scalar quantity - that is, it only has a magnitude. \n\nMagnitude refers to the numerical value or size of a quantity. For example, if we say that a car is moving at a speed of 60 kilometers per hour, the magnitude of its speed is 60.\n\nSpeed describes the rate of change of an object's position over time. \n\nOn the other hand, velocity is a vector quantity - that is, it has both a magnitude and direction. Velocity includes both speed and direction. For example, if you were driving, your speed could be described as 60 miles per hour (mph). But to describe your velocity, you’d need additional information about the direction you were travelling - say 60mph North. \n\n ![Graph](image://6fec459f-94dc-4893-a068-b8bbf43460f3 \"A car driving round a roundabout\")\n\nVectors are more complex than scalars as they involve multiple components instead of just one number or measurement.\n\n","10be6e35-e447-4d78-9bb8-d6360d813339",[144],{"id":145,"data":146,"type":51,"version":25,"maxContentLevel":28},"a0ee50a8-d089-4d33-bb7f-fa7b7affe903",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":147,"binaryCorrect":149,"binaryIncorrect":151},[148],"What kind of value is speed (as opposed to velocity)?",[150],"Scalar",[152],"Vector",{"id":154,"data":155,"type":21,"version":25,"maxContentLevel":28,"pages":157},"f18fc4dc-46e3-4b3f-afc7-397699601d51",{"type":21,"title":156},"Advanced Concepts in Motion",[158,187,203,219],{"id":159,"data":160,"type":25,"maxContentLevel":28,"version":25,"reviews":164},"20650a8b-daae-49da-a92f-bffead13753f",{"type":25,"title":161,"markdownContent":162,"audioMediaId":163},"Acceleration","Acceleration is a change in velocity over time, and it can be caused by either an increase or decrease in speed or a change in direction. It is measured as the rate of change of velocity, usually expressed in meters per second squared (m/s^2). Acceleration can also be described as the rate at which an object's momentum changes - when an object speeds up, its momentum increases; when it slows down, its momentum decreases. If the velocity of a body is decreasing then the acceleration is called retardation.\n\nIn physics, acceleration has many applications such as calculating force from Newton’s Second Law of Motion: F = ma (force equals mass times acceleration). This equation shows that if you want to double the acceleration of an object with constant mass then you will have to double the force applied to it.\n\nInterestingly enough, astronauts experience zero gravity during spaceflight because they are constantly accelerating towards Earth due to gravity, at the same rate as the spacecraft which is carrying them - this phenomenon allows them to float freely inside spacecrafts and perform experiments without being affected by gravitational forces.","44eb5d7c-6fb5-45c6-99e9-f0a5ee629e6a",[165,176],{"id":166,"data":167,"type":51,"version":25,"maxContentLevel":28},"9b062d83-d02f-4f5d-b88b-d4da312ec50d",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":168,"multiChoiceCorrect":170,"multiChoiceIncorrect":172},[169],"How is acceleration typically expressed?",[171],"Meters per second squared (m/s2)",[173,174,175],"Feet per second squared (ft/s2)","Kilometers per second squared (km/s2)","Miles per second squared (mi/s2)",{"id":177,"data":178,"type":51,"version":25,"maxContentLevel":28},"e45306b2-77f9-427d-80d6-d81a16a23e7c",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":179,"multiChoiceCorrect":181,"multiChoiceIncorrect":183},[180],"What equation from Newton's Second Law of Motion shows the relationship between acceleration and force?",[182],"F = ma",[184,185,186],"F = mv","F = me","F = v2",{"id":188,"data":189,"type":25,"maxContentLevel":28,"version":25,"reviews":193},"69f0693d-df1e-4814-aa7f-d9a8fb3b8550",{"type":25,"title":190,"markdownContent":191,"audioMediaId":192},"Kinematic equations","Kinematic equations are mathematical expressions that relate the kinematic variables of time, displacement, constant acceleration and initial and final velocities. These equations can be used to calculate any missing variable when given the other three.\n\n ![Graph](image://582f70f2-a3de-4a1d-8224-53f292a4c6a6 \"People riding a rollercoaster\")\n\nThe most commonly used kinematic equations are those derived from Newton’s Second Law: \n\n1. s = ½at² + v₀t + s₀\n\n2. v² = v₀² + 2as\n\n3. a = Δv/Δt. \n\nThe first equation is useful for calculating displacement over a period of time with constant acceleration, while the second equation is helpful in finding how much an object’s speed changes after a certain distance travelled with constant acceleration. Finally, the third equation allows us to determine an object’s average acceleration by measuring its change in velocity over a period of time.\n\nThese equations have many practical applications such as predicting trajectories or determining how long it will take for objects to reach their destination under different conditions - they even help engineers design roller coasters! Kinematics also plays an important role in robotics where robots must move accurately according to pre-programmed instructions using precise calculations.\n\n","8d7a7860-ae26-4b19-b3d2-e5a80103ea5f",[194],{"id":195,"data":196,"type":51,"version":25,"maxContentLevel":28},"fa42857e-7f75-4aab-916d-0a6847372f96",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":197,"binaryCorrect":199,"binaryIncorrect":201},[198],"Kinematic equations are used to calculate what?",[200],"A third variable, when given the other two",[202],"Two variables, from just the first variable",{"id":204,"data":205,"type":25,"maxContentLevel":28,"version":25,"reviews":209},"b6cc24bf-0aae-4b22-8e9d-939212adb9ac",{"type":25,"title":206,"markdownContent":207,"audioMediaId":208},"Projectile motion","Projectile motion is the motion of an object that has been launched into the air which is subject to gravity. It follows a curved path known as a parabola, which can be described mathematically. The path of an object under projectile motion depends on its initial velocity, angle of launch, and mass.\n\nFor example, if you throw a ball straight up in the air with no spin or other forces acting upon it, it will follow a straight path before returning back to your hand. If you were to throw it at an angle instead, then its trajectory would be slightly different - it would travel further horizontally due to the horizontal component of its initial velocity. This kind of path would be called a parabolic arc.\n\nTo escape the gravitational pull of a body, an object needs to reach ‘escape velocity’. Earth's gravity is inversely proportional to the square of the distance; thus objects far away from our planet experience less gravitational force than those closer by. Projectile motion plays an important role in many aspects of physics such as astronomy and engineering design - for instance rockets are designed based on principles related to this type of motion so that they can reach their intended destination accurately despite external factors.","169eda09-0836-4282-ab42-0a71d78e1e8c",[210],{"id":211,"data":212,"type":51,"version":25,"maxContentLevel":28},"b8b01d15-152f-4cfd-9c86-40d4e16757fe",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":213,"binaryCorrect":215,"binaryIncorrect":217},[214],"What type of path does an object under projectile motion follow?",[216],"Parabola",[218],"Ellipse",{"id":220,"data":221,"type":25,"maxContentLevel":28,"version":25,"reviews":225},"4571cc9e-a4b5-4850-8bc8-60ec5d8a0138",{"type":25,"title":222,"markdownContent":223,"audioMediaId":224},"Relative motion","Relative motion is the motion of an object relative to another object. It is different from absolute motion, which is the motion of an object in relation to a fixed point or frame of reference. For example, if you are standing on a boat that is moving along a river, your position relative to the riverbank will change as the boat moves downstream. This means that although you may not be physically moving yourself, your position relative to other objects around you has changed - this is known as relative motion.\n\nIn physics, it's important to distinguish between these two types of motions when studying forces and their effects on objects. Relative velocity describes how fast one object moves with respect to another; for instance, if two cars are travelling at different speeds side by side then they have different velocities relative to each other even though both cars may be travelling at constant speed in absolute terms. Similarly, acceleration can also be described in terms of its magnitude and direction with respect to another body - this type of acceleration is called centripetal acceleration and it plays an important role in orbital mechanics and satellite navigation systems.\n\nInteresting fact: The fastest recorded speed achieved by any human-made vehicle was 24 kilometers per second (54000 mph) during NASA’s New Horizons mission!\n\n","01f009b0-a31d-45b5-88ab-73f1effc849b",[226],{"id":227,"data":228,"type":51,"version":25,"maxContentLevel":28},"4f7df8a8-691b-40d9-815d-e08e562cfb1b",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":229,"multiChoiceCorrect":231,"multiChoiceIncorrect":233},[230],"What type of acceleration is described in terms of its magnitude and direction with respect to another body?",[232],"Centripetal acceleration",[234,235,236],"Absolute acceleration","Tangential acceleration","Translational acceleration",{"id":238,"data":239,"type":27,"maxContentLevel":28,"version":25,"orbs":242},"104682c9-610c-4725-b2dc-402849b7f6ae",{"type":27,"title":240,"tagline":241},"Newton's Laws of Motion","Newton's system for describing all kinds of motion.",[243,327,380],{"id":244,"data":245,"type":21,"version":25,"maxContentLevel":28,"pages":246},"3b2a95c7-171b-44f9-944e-7ebd3bfb7799",{"type":21,"title":240},[247,263,279,295,310],{"id":248,"data":249,"type":25,"maxContentLevel":28,"version":25,"reviews":253},"739545a3-af6b-4bc3-821e-f96249134ece",{"type":25,"title":250,"markdownContent":251,"audioMediaId":252},"Isaac Newton and his laws of motion","Isaac Newton was an English physicist and mathematician who lived in the 17th century. He is widely regarded as one of the most influential scientists of all time, having made world-changing discoveries in both mathematics and physics. His three laws of motion are fundamental to classical mechanics and form the basis for much of modern engineering.\n\n ![Graph](image://757ebae7-bb4c-4c1d-a93d-d0f089b18356 \"Isaac Newton. Image: I, Sharayanan, CC BY-SA 3.0, via Wikimedia Commons\")\n\nThe first law states that an object will remain at rest or move with a constant velocity unless acted upon by an external force. The second law states that acceleration is proportional to the net force acting on an object. Finally, Newton's third law states that for every action there is always an equal but opposite reaction - meaning when two objects interact they exert equal and opposite forces on each other.\n\nThese laws have been used to explain many phenomena such as why planets orbit around stars, how rockets work, and even why airplanes fly! They are also essential tools for engineers designing machines like cars or robots which must obey these laws in order to function properly. Isaac Newton's three laws of motion provide us with powerful insights into how our universe works and their importance cannot be overstated!\n","11092c6d-16c6-4f5a-8817-436657e5a6cb",[254],{"id":255,"data":256,"type":51,"version":25,"maxContentLevel":28},"84e69e01-edb6-4784-b822-6ae72c5172c5",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":257,"binaryCorrect":259,"binaryIncorrect":261},[258],"What does Newton's third law state?",[260],"For every action there is always equal but opposite reaction",[262],"An object will remain at rest or move with a constant velocity",{"id":264,"data":265,"type":25,"maxContentLevel":28,"version":25,"reviews":269},"bda55429-bf3e-4284-bfc3-64b244e01635",{"type":25,"title":266,"markdownContent":267,"audioMediaId":268},"The first law of motion","Newton's first law of motion states that an object will remain at rest or move with a constant velocity unless acted upon by an external force. This means that if no forces act on an object, it will continue moving in a straight line at the same speed forever - this is known as inertia. \n\n ![Graph](image://a717a17f-95e7-47a5-bab9-4f757ca71426 \"An airplane\")\n\nIn everyday life, we can observe this law when riding in a car; for example, if the brakes are suddenly applied, passengers in a car keep moving and are thrown forward.\n\nThe consequences of Newton's first law have far-reaching implications for our understanding of physics and engineering. For instance, it explains why planets orbit around stars and how rockets work - both rely on objects being propelled through space due to their initial momentum rather than any external force acting upon them. \n\nIt also helps us understand why airplanes fly: air resistance creates lift which counteracts gravity and the balanced forces allow the airplane to keep cruising in a straight line. Additionally, engineers use Newton's first law when designing machines like cars or robots which must obey these laws in order to function properly.\n\n","ef357c91-df07-4141-a65d-5c3c6d8a772f",[270],{"id":271,"data":272,"type":51,"version":25,"maxContentLevel":28},"612832da-b16f-4a3b-a148-aedc83a5b3f2",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":273,"binaryCorrect":275,"binaryIncorrect":277},[274],"What term is used for an object moving in a straight line at the same speed forever?",[276],"Inertia",[278],"Velocity",{"id":280,"data":281,"type":25,"maxContentLevel":28,"version":25,"reviews":285},"704b62b8-8280-473a-b3ab-1072641239f6",{"type":25,"title":282,"markdownContent":283,"audioMediaId":284},"The second law of motion","Newton's second law of motion states that acceleration is proportional to the net force acting on an object, and can be expressed mathematically as F = ma (force equals mass times acceleration). This means that if you apply a certain amount of force to an object, its acceleration will depend on its mass - the more massive it is, the less it will accelerate. To illustrate this concept, consider pushing an empty shopping cart versus pushing a full one: even though both carts are being pushed with the same amount of force, the full cart has greater mass and therefore accelerates at a slower rate.\n\n ![Graph](image://e43c875e-ffd4-4a0f-9705-0aaa01c5d9b9 \"A rocket in the air\")\n\nThis law helps us understand how rockets work - by ejecting fuel outwards at high speeds they create the force thrust which accelerates the rocket and propels it forward against gravity. Engineers use Newton's second law when designing machines like cars or robots to function properly - consider a sports car, which must be as light as possible for maximum acceleration.\n\n","517daaaf-eb4a-4edd-959f-e84248aa0f32",[286],{"id":287,"data":288,"type":51,"version":25,"maxContentLevel":28},"74f52f85-90c5-426d-a405-553b8d6e69fc",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":289,"binaryCorrect":291,"binaryIncorrect":293},[290],"How does the mass of an object affect its acceleration when a certain amount of force is applied?",[292],"The more massive it is, the less it will accelerate",[294],"The more massive it is, the more it will accelerate",{"id":296,"data":297,"type":25,"maxContentLevel":28,"version":25,"reviews":301},"6b19febb-5f8d-4eed-b03c-17c962444cc0",{"type":25,"title":298,"markdownContent":299,"audioMediaId":300},"The third law of motion","Newton’s third law of motion states that for every action there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will also exert an equal but opposite force back onto the first. To illustrate this concept in practice, consider firing a gun: when the bullet is fired from the barrel of the gun it pushes against it with a certain amount of force due to its mass and acceleration; as a result, the gun recoils backwards with an equal but opposite amount of force.\n\n ![Graph](image://f92b9be5-fea5-461a-bf0d-07c4b8aeab9e \"Someone firing a gun\")\n\nThis same principle applies to many other everyday phenomena such as walking or running - each time your foot hits the ground you push off with enough force to propel yourself forward while simultaneously pushing against the ground with an equal and opposite reaction. Similarly, when you jump up into the air you are pushing down on Earth's surface which then pushes back up on you, propelling you into the air. Fascinatingly enough, this simple law has been used for centuries to explain some of nature’s most complex phenomena!\n\n","256b26ee-f06d-4935-baaf-57926ac23d1f",[302],{"id":303,"data":304,"type":51,"version":25,"maxContentLevel":28},"8132763a-57a1-4722-9624-bd962fc53a92",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":305,"multiChoiceCorrect":307,"multiChoiceIncorrect":308},[306],"What law explains the phenomenon of pushing off the ground to propel oneself forward and jumping up into the air?",[298],[266,282,309],"The law of gravity",{"id":311,"data":312,"type":25,"maxContentLevel":28,"version":25,"reviews":316},"f670f4d0-9b25-4728-ada8-1e0f1aa89ae0",{"type":25,"title":313,"markdownContent":314,"audioMediaId":315},"Normal force","The third law of motion states that for every action there is an equal and opposite reaction. \n\nThis same principle applies to normal forces, which are forces exerted by two objects in contact with each other due to their mutual interaction. Normal forces arise from Newton's third law of motion; they act perpendicular (at right angles) to surfaces in contact and oppose any external force applied between them. \n\nFor example, if you press down on a table top then the table will push up against your hand with an equal but opposite normal force - this is why we don't fall through tables! Similarly, when two cars collide head-on at high speed both vehicles experience a large normal force - this helps explain why car crashes can cause so much damage even at relatively low speeds.\n\nNormal forces play an important role in many aspects of physics including mechanics and engineering design; understanding how these forces work allows us to build safer structures like bridges and buildings that can withstand large amounts of stress without collapsing under their own weight or external loads.","f185effa-bab7-4961-905e-44beb99412cb",[317],{"id":318,"data":319,"type":51,"version":25,"maxContentLevel":28},"3fa419bb-a66b-49c7-999a-1ceb7f5a44e8",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":320,"multiChoiceCorrect":322,"multiChoiceIncorrect":323},[321],"What type of force is exerted by two objects in contact with each other due to their mutual interaction?",[313],[324,325,326],"Gravitational force","Centripetal force","Thrust",{"id":328,"data":329,"type":21,"version":25,"maxContentLevel":28,"pages":331},"5013105b-a69d-4a23-9d33-3b8ae0150890",{"type":21,"title":330},"Forces and Motion",[332,350,364],{"id":333,"data":334,"type":25,"maxContentLevel":28,"version":25,"reviews":338},"b0e44b82-e3e4-4ff9-ab30-22c816aab18c",{"type":25,"title":335,"markdownContent":336,"audioMediaId":337},"Friction","Friction is a force that opposes the motion of two objects in contact with each other. It arises from the microscopic irregularities on the surfaces of both objects, which interact and cause resistance to their relative motion. There are two types of friction: static and kinetic. \n\nStatic friction occurs when an object is at rest; it acts to oppose any external force applied to move it, up until a certain threshold point known as the limiting friction or coefficient of static friction. Kinetic friction occurs when an object is already moving; this type of friction acts against its direction of motion and reduces its speed over time until it eventually comes to rest.\n\n ![Graph](image://f33ffcfd-c68c-433d-969e-60d9a959c3fc \"A car nearly slipping off a road\")\n\nThe magnitude (or strength) of these frictional forces depends on several factors such as material composition, normal force between them, and velocity. \n\nFriction plays an important role in many aspects of physics including mechanics and engineering design; understanding how these forces work allows us to build machines like cars that can accelerate quickly without slipping off roads or tracks due to excessive wheel spin caused by too much kinetic friction!\n\n","a07bbbdb-89fa-4c14-959f-1ef82645b107",[339],{"id":340,"data":341,"type":51,"version":25,"maxContentLevel":28},"a9427195-938d-4871-8c25-390e0b301d41",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":342,"multiChoiceCorrect":344,"multiChoiceIncorrect":346},[343],"What are the two types of friction?",[345],"Static and Kinetic",[347,348,349],"Static and Dynamic","Kinetic and Dynamic","Sliding and Rolling",{"id":351,"data":352,"type":25,"maxContentLevel":28,"version":25,"reviews":356},"e6a5a8f9-925b-4328-839c-cf311e5d482a",{"type":25,"title":353,"markdownContent":354,"audioMediaId":355},"Tension","Tension is a force that acts along the length of an object, such as a rope or cable. Tension arises from stretching forces applied to an object and can cause it to elongate or contract depending on the direction and magnitude of the force. In physics, tension plays an important role in understanding how objects move. For example, when a team of huskies pulls a sleigh across snow-covered terrain they exert tension on the sled's harnesses which causes it to accelerate forward due to Newton's second law (F = ma).\n\nTension also has implications for engineering design. Engineers must consider factors such as material strength and elasticity when designing structures like bridges or suspension systems that rely on tension forces for stability. For instance, if too much weight is placed onto one side of a bridge then this could cause excessive strain on certain parts leading them to break under their own weight. Similarly, cars with faulty suspension systems may experience uneven tire wear due to unequal distribution of load between tires caused by inadequate tensioning forces. Understanding these principles allows us to build safer machines and structures that can withstand external loads without breaking apart.","7809925f-700c-469b-9a6a-38b8865c0355",[357],{"id":358,"data":359,"type":51,"version":25,"maxContentLevel":28},"29b09fa0-a439-44a8-bb7e-e4071e3fa12f",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":360,"binaryCorrect":362,"binaryIncorrect":363},[361],"What physical force acts along the length of an object, such as a rope or cable?",[353],[335],{"id":365,"data":366,"type":25,"maxContentLevel":28,"version":25,"reviews":370},"299dfe8f-9406-40c5-912f-4cb0516e0cd9",{"type":25,"title":367,"markdownContent":368,"audioMediaId":369},"Applications of Newton's laws","Newton's laws of motion are fundamental to the study of physics and have a wide range of applications in everyday life. In mechanics, Newton's second law (F = ma) is used to calculate forces acting on objects such as cars or airplanes, allowing engineers to design vehicles that can safely reach their destination. In sports, athletes use Newton's third law (action-reaction) when throwing a ball or swinging a bat; the force exerted by the athlete is equal and opposite to the force exerted by the ball or bat upon them. And Newton’s laws are applied throughout medicine, particularly in the field of biomechanics which investigates how forces affect the bones, tendons and ligaments in our bodies.\n\n ![Graph](image://8957274c-cd20-4e8a-8d07-3b0c9afb03e0 \"An athlete swinging a bat\")\n\nIn addition, understanding how these laws work allows us to develop new technologies such as robots which rely on precise calculations for movement and navigation. For example, NASA’s Curiosity rover uses its onboard computer system powered by algorithms based on Newton’s laws of motion in order to traverse Mars' terrain autonomously! Without our knowledge of these basic physical principles we would not be able to make advances in technology nor understand many aspects of our world today.\n","41b13c48-3a1f-4670-8e72-f975ffb806e6",[371],{"id":372,"data":373,"type":51,"version":25,"maxContentLevel":28},"f7d94a7a-0e94-42ad-af12-71eda1b871a1",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":374,"binaryCorrect":376,"binaryIncorrect":378},[375],"In which field are Newton's laws of motion applied to study how forces affect the bones, tendons and ligaments in our bodies?",[377],"Biomechanics",[379],"Kinesiology",{"id":381,"data":382,"type":21,"version":25,"maxContentLevel":28,"pages":384},"7fe68b0c-da7a-46de-999f-557bc8d7c0ca",{"type":21,"title":383},"Gravitational Principles",[385,401],{"id":386,"data":387,"type":25,"maxContentLevel":28,"version":25,"reviews":391},"949e3fa4-4ab4-4cc3-93df-01fa6dc03d9a",{"type":25,"title":388,"markdownContent":389,"audioMediaId":390},"Newton’s law of universal gravitation","Newton's law of universal gravitation states that every object in the universe attracts every other object with a force proportional to their masses and inversely proportional to the square of the distance between them. This means that objects with greater mass will exert a stronger gravitational pull than those with less mass, regardless of their size or shape. For example, Earth has much more mass than its moon, so it exerts a much stronger gravitational pull on it.\n\n ![Graph](image://22bd62bf-3fdf-4a33-b788-2b98bc095db5 \"A cluster of galaxies. Image: NASA Hubble, CC BY 2.0, via Wikimedia Commons\")\n\nThis law explains why objects fall towards each other when released from rest; they are attracted by gravity. It also explains why planets orbit around stars and why galaxies form clusters - all due to the attractive forces between them. Furthermore, this law helps us understand how weight is related to an object’s mass: an object’s weight is determined by its mass multiplied by the acceleration due to gravity at any given location (9.8 m/s2 on Earth). Therefore, if you take two identical objects but place one on Earth and one on Mars (where g = 3.7 m/s2), then they would have different weights even though they have equal masses!\n\n","18d461c5-fdd0-4ede-bb86-f361c69cb794",[392],{"id":393,"data":394,"type":51,"version":25,"maxContentLevel":28},"f032a379-39c5-4fb5-9f34-c61fbd9cfc50",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":395,"binaryCorrect":397,"binaryIncorrect":399},[396],"How does Newton's law of universal gravitation explain why objects fall towards each other when released from rest?",[398],"They are attracted by gravity",[400],"They are repelled by gravity",{"id":402,"data":403,"type":25,"maxContentLevel":28,"version":25,"reviews":407},"25b65b81-4873-4495-aa5f-84c906f710c4",{"type":25,"title":404,"markdownContent":405,"audioMediaId":406},"Elastic and inelastic collisions","Elastic collisions are those in which the kinetic energy of the objects involved is conserved. This means that, after the collision, both objects will have the same total amount of kinetic energy as before. In contrast, inelastic collisions involve a loss of energy due to some form of deformation or friction between the two objects. \n\n ![Graph](image://152ea5f4-d027-4cff-9068-f35928c5c01e \"Elastic collisions\")\n\nYou can see a near-elastic collision at play in a Newton's cradle - when one ball at one end is pulled back and released, it collides with another ball on the other side and transfers its momentum to it with only a small loss in kinetic energy. This motion is then passed along to swing the ball at the other end of the row - and so on. \n\n\n\n\n\n","314db950-f937-4cb6-81ef-5f5ef22fcebb",[408],{"id":409,"data":410,"type":51,"version":25,"maxContentLevel":28},"4981c6b6-6c2b-4f13-82a5-5a989ea270d5",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":411,"multiChoiceCorrect":413,"multiChoiceIncorrect":415},[412],"What type of collision is demonstrated in a Newton's cradle experiment?",[414],"Elastic collision",[416,417,418],"Inelastic collision","Momentum collision","Velocity collision",{"id":420,"data":421,"type":27,"maxContentLevel":28,"version":25,"orbs":424},"d81c5bf9-bafe-4136-879c-df7e1dda7747",{"type":27,"title":422,"tagline":423},"Work and Energy","How work works.",[425,519],{"id":426,"data":427,"type":21,"version":25,"maxContentLevel":28,"pages":429},"2e510928-4c3e-4394-b8f0-84d4a887bfb5",{"type":21,"title":428},"Fundamentals of Work and Energy",[430,448,466,484,501],{"id":431,"data":432,"type":25,"maxContentLevel":28,"version":25,"reviews":436},"1876e87f-507e-49b6-b1b4-88bc3759e8b7",{"type":25,"title":433,"markdownContent":434,"audioMediaId":435},"What is work","Work is a fundamental concept in physics, and it can be defined as the transfer of energy from one object to another by the application of force. Work is done when an external force causes an object to move or change its shape. The amount of work done on an object depends on the magnitude of the force applied and the distance over which it acts. For example, if you lift a box up two meters with a force of 10 Newtons (N), then you have done 20 joules (J) of work – 10 N multiplied by 2 m.\n\n ![Graph](image://f576af10-bd74-4b62-a406-1400c0e0c546 \"A man at work\")\n\nWork can be positive, negative or zero. If an object is moved in the same direction as the applied force, the work is positive. If the object is moved in the opposite direction to the applied force, the work is negative. And if the object does not move, zero work has been done - if you push against a wall for a long time, you might use a lot of energy but unless you manage to move the wall you have done zero work.\n\n","9c160146-dd3f-4e91-a67f-dbcb37336554",[437],{"id":438,"data":439,"type":51,"version":25,"maxContentLevel":28},"b1a4c3fa-250b-42f5-857d-601a27e320a0",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":440,"multiChoiceCorrect":442,"multiChoiceIncorrect":444},[441],"How much work is done when a force of 10 Newtons (N) is applied to an object that is moved two meters?",[443],"20 joules (J)",[445,446,447],"10 joules (J)","30 joules (J)","40 joules (J)",{"id":449,"data":450,"type":25,"maxContentLevel":28,"version":25,"reviews":454},"7e44a16d-b557-4951-a822-042ba2e90298",{"type":25,"title":451,"markdownContent":452,"audioMediaId":453},"Work-energy theorem","The work-energy theorem states that the total work done by the forces on an object is equal to the change in its kinetic energy. This means that when a force acts upon an object, it does work and increases or decreases its kinetic energy accordingly. \n\nThis relationship between work and energy can be used to calculate how much power is required for certain tasks. Power is defined as the rate at which work is done, usually expressed in watts (W). To calculate power, divide the amount of work done by time taken; for instance, if you lifted a box up two meters with a force of 10 N over five seconds, then your power output would be 4 W (20 J divided by 5 s). The higher the power output, the faster an object will move or accelerate given enough time. In fact, one watt is equivalent to one joule per second.","80022a2f-6973-4f68-b917-d758264e8156",[455],{"id":456,"data":457,"type":51,"version":25,"maxContentLevel":28},"fe5692d3-0172-4443-9a88-a56c80709bf8",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":458,"multiChoiceCorrect":460,"multiChoiceIncorrect":462},[459],"What is the unit of power, usually expressed in watts (W)?",[461],"Joules per second",[463,464,465],"Joules per minute","Joules per hour","Joules per day",{"id":467,"data":468,"type":25,"maxContentLevel":28,"version":25,"reviews":472},"61821bd6-4905-4879-b132-54fde965a23a",{"type":25,"title":469,"markdownContent":470,"audioMediaId":471},"Kinetic energy"," ![Graph](image://cdf6e322-2163-44e0-8891-6e6113835c4e \"A tree in the fall\")\n\nKinetic energy is the energy of motion, and it can be found in any object that is moving. It is calculated by multiplying half an object's mass with its velocity squared (KE = ½mv²). Kinetic energy increases as an object moves faster, so a car travelling at 100 km/h has more kinetic energy than one travelling at 50 km/h.\n\nThe relationship between work and kinetic energy can be seen when a force acts upon an object to cause it to move or accelerate; this force does work on the object which increases its kinetic energy accordingly. For example, when you push a box across the floor, your pushing force does work on the box which causes it to move and increase its kinetic energy. \n\nKinetic energy can also be found in everyday objects such as leaves falling from trees or rockets blasting off into space. The amount of kinetic energy possessed by each depends on their mass and speed. For instance, a rocket blasting off will have much greater amounts than a leaf floating down from a tree due to its higher speed.\n\n","4735ed66-086c-4b6c-a27b-c69b16dd405f",[473],{"id":474,"data":475,"type":51,"version":25,"maxContentLevel":28},"5708ee76-5ea8-4c10-9dfe-6ce4c727ef9b",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":476,"multiChoiceCorrect":478,"multiChoiceIncorrect":480},[477],"How is kinetic energy calculated?",[479],"KE = ½mv²",[481,482,483],"KE = mv²","KE = ½mv","KE = mv",{"id":485,"data":486,"type":25,"maxContentLevel":28,"version":25,"reviews":490},"c3c373ab-8b16-49b5-b465-afa0f66c79cd",{"type":25,"title":487,"markdownContent":488,"audioMediaId":489},"Potential energy","Potential energy is the stored energy of an object due to its position, configuration, electrical charge and other factors. It can be released and converted into kinetic energy when a force such as gravity acts upon it. Potential energy is related to work in that it requires work to move an object from one potential state to another; for example, lifting a heavy box up onto a shelf requires work which increases the box's potential energy.\n\nGravitational potential energy is the amount of stored energy an object has due to its height above Earth’s surface – the higher up it is, the more gravitational potential energy it has. \n\nElastic potential energy refers to objects that are stretched or compressed beyond their natural shape and have built-up tension ready for release; rubber bands and springs are examples of this type of potential energy. \n\nChemical potential energies come from chemical bonds between atoms in molecules; these bonds store large amounts of latent heat which can be released through combustion reactions like burning wood or gasoline.","24547946-49b0-442c-85fe-e852848e744c",[491],{"id":492,"data":493,"type":51,"version":25,"maxContentLevel":28},"3a696089-9e72-46f6-97f9-ddcc74b0be40",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":494,"multiChoiceCorrect":496,"multiChoiceIncorrect":497},[495],"What type of energy is related to work, as it requires work to move an object from one state to another?",[487],[498,499,500],"Heat energy","Chemical energy","Electrical energy",{"id":502,"data":503,"type":25,"maxContentLevel":28,"version":25,"reviews":507},"8f561472-8513-4b44-b35d-df6b94f8a1ab",{"type":25,"title":504,"markdownContent":505,"audioMediaId":506},"Conservation of energy","The law of conservation of energy states that the total amount of energy in a closed system remains constant. This means that potential and kinetic energies can be converted from one form to another, but the total amount will always remain the same. \n\nFor example, when a ball is thrown into the air it gains gravitational potential energy as it rises, while it slows down and its kinetic energy decreases. When it reaches its highest point and begins to fall back down again, its gravitational potential energy is converted into kinetic energy until it hits the ground.\n\n ![Graph](image://ffc9a531-ddeb-4276-93ce-69afec8381ac \"A ball being thrown into the air.\")\n\nThis law has far-reaching implications for physics: all forms of motion are governed by this principle - from planets orbiting stars to electrons moving around atoms. In addition to explaining physical phenomena on Earth and beyond our atmosphere, this law also helps us understand everyday occurrences like roller coasters at amusement parks – these rides use stored mechanical potential energies which are then released through gravity and friction during their descent down hills and loops!\n\n","e733e286-4012-4e07-b917-ffbec400be2d",[508],{"id":509,"data":510,"type":51,"version":25,"maxContentLevel":28},"21fb459b-5d4e-4e28-9a2b-0ce93b878e54",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":511,"multiChoiceCorrect":513,"multiChoiceIncorrect":515},[512],"What law states that the total amount of energy in a closed system remains constant?",[514],"The Law of Conservation of Energy",[516,517,518],"The Law of Gravity","The Law of Motion","The Law of Thermodynamics",{"id":520,"data":521,"type":21,"version":25,"maxContentLevel":28,"pages":523},"53f6fcf5-2d4a-4ce4-9c5e-fb3b50c37449",{"type":21,"title":522},"Advanced Concepts in Work and Energy",[524,542,558,576,594],{"id":525,"data":526,"type":25,"maxContentLevel":28,"version":25,"reviews":530},"20b397f0-ad17-4bfa-8b98-26977e4895a4",{"type":25,"title":527,"markdownContent":528,"audioMediaId":529},"Work done by a constant force","Work done by a steady, unchanging (constant) force, is straightforward to calculate. This type of work can be calculated using the equation W = Fd, where F is the magnitude of the applied force and d is displacement. \n\nFor example, if a person pushes a box with 10 Newtons (N) of force for 2 meters (m), then they have done 20 Joules (J) worth of work on that box.\n\n ![Graph](image://74472e64-8036-461b-ac1c-cae05a2018e9 \"A game of tug of war\")\n\nThe concept of work done by a constant force also applies to the rotational motion, such as when turning a wheel or cranking an engine. In this case, torque - which is equal to force multiplied by distance from pivot point - replaces force in our equation: W = τθ, where τ represents torque and θ represents angular displacement in radians. \n\nFor instance, if you apply 5 Nm (Newton-meters) worth of torque to turn a wheel through 1.5708 radians (equivalent to 90 degrees) then you have done 450 J worth of work on it!\n\n","3fedc75a-23dc-4537-ae9a-87439c873f1a",[531],{"id":532,"data":533,"type":51,"version":25,"maxContentLevel":28},"30434a78-6dac-4f96-8e9c-3fe1190aebf2",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":534,"multiChoiceCorrect":536,"multiChoiceIncorrect":538},[535],"How is work done by a constant force calculated for rotational motion?",[537],"W = τθ",[539,540,541],"W = Fd","W = Fθ","W = τd",{"id":543,"data":544,"type":25,"maxContentLevel":28,"version":25,"reviews":548},"ffa152c4-981c-4cae-882c-63e74120bbe8",{"type":25,"title":545,"markdownContent":546,"audioMediaId":547},"Work done by a variable force","Work done by a variable force is more complex than work done by a constant force, as the magnitude of the applied force changes over time. This means that equations such as W = Fd and W = τθ are not applicable in this case, since they assume that the applied force remains constant throughout. To calculate work done by a variable force, we must use integration – an advanced mathematical technique which involves summing up all of the small changes in energy over time to get an overall result.\n\n ![Graph](image://b0a7ea66-671d-4884-a4c5-3d10637eb6e7 \"Someone pushing a box across a room\")\n\nIntegration allows us to take into account any changes in velocity or acceleration during motion, making it possible to accurately calculate work done even when forces vary with time. For example, if you were pushing a box across a room at varying speeds then integration would allow you to determine how much total energy was transferred from your body to the box during its journey. Similarly, if you were turning a wheel at different rates then integration could be used to find out how much total torque was applied over its rotation angle. Integration is thus essential for calculating work done by variable forces and understanding their effects on objects!\n\n","5b10049a-ebbe-4338-80ce-34735a34ab8d",[549],{"id":550,"data":551,"type":51,"version":25,"maxContentLevel":28},"64edcb92-b66d-4951-8a72-2c7d85fed44f",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":552,"binaryCorrect":554,"binaryIncorrect":556},[553],"What mathematical technique is used to calculate work done by a variable force?",[555],"Integration",[557],"Differentiation",{"id":559,"data":560,"type":25,"maxContentLevel":28,"version":25,"reviews":564},"27d3bcb9-415f-478e-8a5c-9b164e0eb5c2",{"type":25,"title":561,"markdownContent":562,"audioMediaId":563},"Power","Power is the rate at which work is done, and can be calculated by dividing the amount of work done by the time taken to do it. Power is usually expressed in watts (W), with one watt being equal to one joule per second. A modern light bulb typically uses around 10 W of power, while a lightning bolt can have up to 10 billion W!\n\nThe power output of an object or system depends on its efficiency – how much of its energy input it converts into useful output. The most efficient systems are those that convert all their input energy into useful output: a 100% efficient engine would convert all fuel used into motion. However, no real-world system has perfect efficiency; even the best engines only achieve around 40-50%. Some energy will always be lost as heat or sound during operation.\n\n ![Graph](image://88fc936c-1d2e-4b8f-8554-0a2fd0c453f9 \"A lightning bolt\")\n\nPower also depends on factors such as friction and air resistance which reduce an object's speed over time and thus decrease its overall power output. To counteract these effects engineers must design machines with low drag coefficients and high torque outputs in order to maximize their efficiency and performance.\n\n","9f0bd3b3-6054-4ba3-ae9d-220129861e04",[565],{"id":566,"data":567,"type":51,"version":25,"maxContentLevel":28},"44b2ef3a-8b16-44ff-8a77-612ecda7fa5f",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":568,"multiChoiceCorrect":570,"multiChoiceIncorrect":572},[569],"What is the unit of power typically expressed in?",[571],"Watts (W)",[573,574,575],"Joules (J)","Kilowatts (kW)","Amperes (A)",{"id":577,"data":578,"type":25,"maxContentLevel":28,"version":25,"reviews":582},"c76f3cc6-e502-40c1-a614-db2e06144d35",{"type":25,"title":579,"markdownContent":580,"audioMediaId":581},"Mechanical energy","Mechanical energy is the combination of potential and kinetic energy.\n\nPotential energy is stored in an object due to its position or configuration, while kinetic energy is the energy of motion. When these two energies are combined they create mechanical energy, which can be used to do work.\n\n ![Graph](image://e147d8e0-d30e-4323-a155-a1f50d0c6268 \"Someone cycling\")\n\nFor example, when a roller coaster car climbs up a hill it gains potential energy as it rises higher above the ground; this potential energy then converts into kinetic energy as it descends down the other side and accelerates towards its final destination. \n\nThe sum of these two energies makes up the mechanical energy and the mechanical power that propels the car along its track. The amount of mechanical power available depends on how much potential and kinetic energies are present in a system at any given time; for instance if there is more potential than kinetic energy then acceleration will be slower.\n\n","6be7d94e-4e8a-4c01-b123-f4b560af0968",[583],{"id":584,"data":585,"type":51,"version":25,"maxContentLevel":28},"8d5bbfe8-d43c-4076-9978-a6b2c791ed6d",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":586,"multiChoiceCorrect":588,"multiChoiceIncorrect":590},[587],"How is mechanical energy calculated?",[589],"By combining potential and kinetic energy",[591,592,593],"By using work and energy","By converting kinetic energy into potential energy","By converting potential energy into kinetic energy",{"id":595,"data":596,"type":25,"maxContentLevel":28,"version":25,"reviews":600},"8d43eda9-6707-4c07-9c18-5cc8a222e8ce",{"type":25,"title":597,"markdownContent":598,"audioMediaId":599},"Thermal energy and temperature","Thermal energy is the energy of random motion of particles. Temperature is a measure of how much thermal energy an object contains; as temperature increases, so does the average kinetic energy of its particles. Heat is the transfer of thermal energy from one object to another due to a difference in their temperatures. \n\nThis process occurs when two objects with different temperatures come into contact with each other until they reach equilibrium - that is, until both objects have the same temperature.\n\n ![Graph](image://6b9612ba-8f49-437c-9625-8fc33f414d71 \"Friction being created with hands\")\n\nHeat can be converted into work using a heat engine: when fuel combusts in an engine it releases heat which then causes pistons to move and generate mechanical power. \n\nWork can also be converted into heat - Consider how rubbing your hands together quickly creates friction which generates heat and warms them up! Work can be completely converted into heat but heat can only be partially converted into work.\n\n\n\n\n\n","4465910c-c505-4217-b8c4-6ccc37f54a4c",[601],{"id":602,"data":603,"type":51,"version":25,"maxContentLevel":28},"32615e3c-c217-4ed1-a927-bc718262c5d4",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":604,"multiChoiceCorrect":606,"multiChoiceIncorrect":608},[605],"What is the process that occurs when two objects with different temperatures come into contact with each other until they reach equilibrium?",[607],"Heat transfer",[609,610,611],"Work conversion","Heat conversion","Thermal equilibrium",{"id":613,"data":614,"type":27,"maxContentLevel":28,"version":25,"orbs":617},"82fea5d7-f269-41c0-9a7d-003d2e1ec404",{"type":27,"title":615,"tagline":616},"Relativity and space-time","How relativity starts to unravel Newtonian mechanics.",[618,694,749],{"id":619,"data":620,"type":21,"version":25,"maxContentLevel":28,"pages":622},"397d243e-5120-4f54-80cc-33751a6d58bc",{"type":21,"title":621},"Foundations of Relativity",[623,641,659,677],{"id":624,"data":625,"type":25,"maxContentLevel":28,"version":25,"reviews":629},"9342cf16-b288-4db0-97c9-25a2779cfee8",{"type":25,"title":626,"markdownContent":627,"audioMediaId":628},"Introduction to Relativity Theory: The Historical Context","The theory of relativity is one of the most important scientific discoveries in history, and its implications have revolutionized our understanding of space and time. Developed by Albert Einstein in 1905, it was a radical departure from Newtonian mechanics which had been accepted for centuries prior. The theory states that the laws of physics are the same for all observers in a non-accelerating frame of reference. One consequence is that time and space can be seen as different dimensions of a single continuum known as spacetime. \n\n ![Graph](image://9fb511b7-87bf-49d8-a57d-74ff1c4079ed \"Albert Einstein\")\n\nEinstein's work was revolutionary because it challenged long-held beliefs about how physical systems worked. His theories were initially met with skepticism but gained acceptance after being tested through experiments such as measuring light deflection around massive objects like galaxy clusters, stars, or black holes. Today, relativity forms the basis for much modern research into astrophysics and cosmology, providing us with insights into some of nature’s greatest mysteries including dark matter and dark energy.\n\n","8ef7d8cc-c09f-4c0d-8d78-355db811202a",[630],{"id":631,"data":632,"type":51,"version":25,"maxContentLevel":28},"ba130d1c-10fa-4c08-bbab-5ac60484007b",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":633,"multiChoiceCorrect":635,"multiChoiceIncorrect":637},[634],"What is the name of the scientific theory developed by Albert Einstein in 1905 which revolutionized our understanding of space and time?",[636],"Theory of Relativity",[638,639,640],"Theory of Gravity","Theory of Motion","Theory of Quantum Mechanics",{"id":642,"data":643,"type":25,"maxContentLevel":28,"version":25,"reviews":647},"f2b38b19-4da9-4aa2-a2f2-59df198708f6",{"type":25,"title":644,"markdownContent":645,"audioMediaId":646},"The Postulates of Special Relativity","The postulates of special relativity are the two fundamental principles from which all other aspects of the theory derive. The first is known as the Principle of Relativity, which states that physical laws remain unchanged in any inertial reference frame - that is, provided the frame of reference is not accelerating. \n\n\n ![Graph](image://3e27c1f6-d286-4658-a365-ab5f238bbeb6 \"Einstein’s Theory of Special Relativity\")\n\nThe second postulate is known as the Speed of Light Postulate and states that light travels at a constant speed regardless of its source or observer's motion relative to it. This means that if two observers measure the speed of light emitted from a single source, they will both measure it to be exactly 299 792 458 meters per second - even if one observer is moving towards or away from it! This has been confirmed by numerous experiments over time and forms an integral part of Einstein’s Theory of Special Relativity. Special relativity has some strange and surprising consequences: it means, for example, that events which appear simultaneous to one observer may not appear so to another depending on their relative velocity.\n","60e0977f-866e-4115-8250-15cc486cbab8",[648],{"id":649,"data":650,"type":51,"version":25,"maxContentLevel":28},"ab3eb141-d994-4093-b258-3065de4ee900",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":651,"multiChoiceCorrect":653,"multiChoiceIncorrect":655},[652],"What is the constant speed of light, regardless of the source or observer's motion relative to it?",[654],"299 792 458 meters per second",[656,657,658],"299 792 458 kilometers per second","299 792 458 feet per second","299 792 458 miles per second",{"id":660,"data":661,"type":25,"maxContentLevel":28,"version":25,"reviews":665},"8c7b8c75-6842-4d28-8cd8-5743ed8dfe67",{"type":25,"title":662,"markdownContent":663,"audioMediaId":664},"Time Dilation and Length Contraction"," ![Graph](image://474c2783-7fee-47f0-962b-6bff586000dd \"An atomic clock\")\n\nTime dilation and length contraction are two of the most fascinating effects of relativity. They occur when objects move at relativistic speeds - which are speeds comparable to the speed of light. Time dilation is the phenomenon whereby time passes more slowly for an object in motion relative to a stationary observer; this means that if you were travelling on a spaceship moving close to the speed of light, your clock would appear to tick slower than someone observing a clock on Earth. This effect has been confirmed by numerous experiments such as the Hafele–Keating experiment conducted with atomic clocks aboard airplanes flying around the world.\n\nLength contraction is another remarkable consequence of relativity, where a moving object's length appears shorter than its length at rest when measured by an observer. For example, if you were standing still while watching a train pass by at near-light speeds, it would appear much shorter than its actual size due to its rapid movement relative to you.\n\n","c3adce57-fbb7-4271-8584-362dce143382",[666],{"id":667,"data":668,"type":51,"version":25,"maxContentLevel":28},"a48df5b8-721a-4f1c-be99-0ef90700e54e",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":669,"multiChoiceCorrect":671,"multiChoiceIncorrect":673},[670],"What experiment was conducted to confirm the phenomenon of time dilation?",[672],"The Hafele–Keating experiment",[674,675,676],"The Michelson–Morley experiment","The Kennedy–Khrushchev experiment","The Hubble–Kepler experiment",{"id":678,"data":679,"type":25,"maxContentLevel":28,"version":25,"reviews":683},"c2497e8d-29bc-47a7-95ba-a272dd9f048e",{"type":25,"title":680,"markdownContent":681,"audioMediaId":682},"The Twin Paradox: An Illustration of Time Dilation"," ![Graph](image://35ca969e-cfe5-46b8-a27b-e945cf7f0aa2 \"Alpha Centauri\")\n\nThe Twin Paradox is a thought experiment that illustrates the effects of time dilation in relativity. It involves two twins, one of whom travels away from Earth at near-light speeds and returns after some time has passed. \n\nUpon their reunion, the travelling twin will have aged less than their stay-at-home sibling due to the effects of time dilation. Depending on the speed of travel, one twin will in effect now be months, years, or even centuries younger than the other. \n\nThis phenomenon can be explained mathematically using Lorentz transformations and has been verified through experiments involving high-speed particles in particle accelerators.\n\nIn addition to being an interesting illustration of relativistic phenomena, this paradox also serves as a reminder that our perception of time is relative; what may seem like a long period for one observer could appear much shorter for another depending on their motion relative to each other.\n\n","5113e7b7-19d5-4243-9df7-b98ee7762719",[684],{"id":685,"data":686,"type":51,"version":25,"maxContentLevel":28},"85108e9a-5065-4367-a295-f9c649e8d763",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":687,"multiChoiceCorrect":689,"multiChoiceIncorrect":691},[688],"What phenomenon can be explained mathematically using Lorentz transformations and has been verified through experiments involving high-speed particles in particle accelerators?",[690],"Time dilation",[692,615,693],"The Twin Paradox","Perception of time",{"id":695,"data":696,"type":21,"version":25,"maxContentLevel":28,"pages":698},"c7bc52ca-f2d7-40e2-bd04-369f155b9314",{"type":21,"title":697},"General Relativity and Its Principles",[699,717,733],{"id":700,"data":701,"type":25,"maxContentLevel":28,"version":25,"reviews":705},"1d6fdb19-0473-4840-9b32-5a69d9e7ec6d",{"type":25,"title":702,"markdownContent":703,"audioMediaId":704},"The Equivalence Principle and General Relativity","The Equivalence Principle, proposed by Albert Einstein in 1907, states that the effects of gravity and acceleration are indistinguishable. This means that an observer cannot tell whether they are being accelerated or if they are experiencing a gravitational field. This principle is closely related to General Relativity, which explains gravitation as a consequence of the curvature of space-time caused by mass and energy.\n\n ![Graph](image://32096d51-6f3f-4c42-ad66-f38f37ede57e \"Loránd Eötvös\")\n\nGravitational mass is defined as the mass of an object which determines its interactions with a gravitational field - the mass which gravity acts upon. Inertial mass, on the other hand, measures how much resistance an object has to changes in its motion when acted upon by a force. \n\nAccording to General Relativity, these two masses must be equal for all objects; this was confirmed experimentally with high precision using torsion balances such as those developed by Loránd Eötvös between 1885 and 1909.\n\n","16d6f43a-10f3-4e8a-bc6f-a9280e118cc9",[706],{"id":707,"data":708,"type":51,"version":25,"maxContentLevel":28},"a427f770-9b8d-43a4-9637-d0507ab5bb4f",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":709,"multiChoiceCorrect":711,"multiChoiceIncorrect":713},[710],"What is the principle proposed by Albert Einstein that states the effects of gravity and acceleration are indistinguishable?",[712],"The Equivalence Principle",[714,715,716],"The Inertial Principle","The Mass Principle","The Relativity Principle",{"id":718,"data":719,"type":25,"maxContentLevel":28,"version":25,"reviews":723},"b66655bf-3fa7-47f7-9119-4f617c04e0b2",{"type":25,"title":720,"markdownContent":721,"audioMediaId":722},"Space-Time and Spacetime Diagrams: Representing Relativity Graphically","The space-time continuum is a mathematical model that combines the three dimensions of space with the fourth dimension of time, allowing us to represent events in four-dimensional spacetime diagrams. \n\nThese diagrams are used to illustrate how objects move through space and time relative to each other, as well as how gravity affects their motion. For example, when two objects interact gravitationally, they follow curved paths in spacetime due to the curvature caused by their masses. \n\nThis phenomenon can be seen in binary star systems where stars orbit around each other along elliptical trajectories.\n\n ![Graph](image://27209a9b-16ee-4d2e-90f4-3e9bb062f085 \"A person standing still and watching a train pass by\")\n\nSpacetime diagrams also help us visualize phenomena such as time dilation and length contraction which occur when an object moves close to light speed relative to another observer. \n\nThe most familiar spacetime diagrams are known as Minkowski diagrams after their creator Hermann Minkowski who first developed them in 1908. \n\nAn alternative version, the Loedel diagram, can make it easier to see the equivalence of two different reference frames which is postulated by special relativity.\n\n","4273847d-7f03-4c79-81d4-04291e0e8d8a",[724],{"id":725,"data":726,"type":51,"version":25,"maxContentLevel":28},"bc37c0b9-85f1-4546-aa33-74f06ada0ffd",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":727,"multiChoiceCorrect":729,"multiChoiceIncorrect":731},[728],"Who first developed spacetime diagrams in 1908?",[730],"Hermann Minkowski",[74,732,72],"Stephen Hawking",{"id":734,"data":735,"type":25,"maxContentLevel":28,"version":25,"reviews":739},"b262fb6c-6497-42d0-ade9-a521b8d60a0c",{"type":25,"title":736,"markdownContent":737,"audioMediaId":738},"Black Holes and Gravitational Waves"," ![Graph](image://5e857593-5b28-4af4-b60c-0d18afaec5b5 \"A black hole\")\n\nBlack holes are regions of spacetime where gravity is so strong that nothing, not even light, can escape its pull. They form when a massive star collapses in on itself due to the force of its own gravity. General Relativity predicts that black holes should exist and emit gravitational waves as they interact with other objects in space. These waves are ripples in spacetime caused by accelerating masses such as two orbiting black holes or neutron stars spiralling towards each other.\n\nGravitational waves were predicted by Einstein's theory over 100 years ago but only recently observed for the first time in 2015 using the Laser Interferometer Gravitational-Wave Observatory (LIGO). This breakthrough was awarded the 2017 Nobel Prize in Physics and has opened up an entirely new field of astronomy known as gravitational wave astronomy which allows us to observe events happening at extreme distances from Earth. The detection of these waves also confirms one of Einstein’s most famous predictions: that mass warps spacetime!\n","1deedb0f-d821-4d39-a881-eb2603d4e8b6",[740],{"id":741,"data":742,"type":51,"version":25,"maxContentLevel":28},"e5d7fe17-d36a-43ce-bf11-7a2c447d3738",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":743,"binaryCorrect":745,"binaryIncorrect":747},[744],"What year were gravitational waves first observed?",[746],"2015",[748],"2017",{"id":750,"data":751,"type":21,"version":25,"maxContentLevel":28,"pages":753},"8612963f-e3b1-4ca0-9964-12e3e9f03f68",{"type":21,"title":752},"Experimental and Observational Evidence",[754,772,788],{"id":755,"data":756,"type":25,"maxContentLevel":28,"version":25,"reviews":760},"ee01681b-dd1b-4032-a23d-f043bf250212",{"type":25,"title":757,"markdownContent":758,"audioMediaId":759},"Experimental Tests of Relativity","The Michelson-Morley experiment of 1887 was the first attempt to measure the speed of light in a vacuum, and it provided evidence that contradicted the scientists’ preferred theory that light waves travelled through a medium called aether. \n\nThe experiment showed that light travels at a constant speed regardless of its direction or the motion of its source, which is now known as the Principle of Relativity. This principle forms one of the foundations for Einstein's Theory of Relativity.\n\n ![Graph](image://a8b9a93f-7949-431d-9024-5d8aeaab996d \"The Michelson-Morley experiment\")\n\nIn 1915, Einstein proposed his General Theory of Relativity which predicted that gravity affects spacetime itself and causes objects to move along curved paths instead of straight lines. To test this theory, scientists have conducted experiments such as measuring how much time passes on Earth compared to an orbiting satellite or using laser interferometers like LIGO (Laser Interferometer Gravitational-Wave Observatory) to detect gravitational waves from distant sources such as two merging black holes. \n\nThese experiments have confirmed predictions made by General Relativity including time dilation due to relative motion between observers, and they have opened up entirely new fields in astronomy such as gravitational wave astronomy.\n\n","7f87252f-c0c9-4947-8877-27fd5ac1036b",[761],{"id":762,"data":763,"type":51,"version":25,"maxContentLevel":28},"8097490f-a8b9-4dad-b792-8b9f4f07a2df",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":764,"multiChoiceCorrect":766,"multiChoiceIncorrect":768},[765],"What experiment in 1887 provided evidence that contradicted the scientists’ preferred theory about light waves?",[767],"Michelson-Morley experiment",[769,770,771],"The LIGO experiment","General Relativity Trial","Matthew-Monahan experiment",{"id":773,"data":774,"type":25,"maxContentLevel":28,"version":25,"reviews":778},"8d489d44-4034-4954-ac32-b83af20a9eb4",{"type":25,"title":775,"markdownContent":776,"audioMediaId":777},"Alternative Theories of Gravity","Although general relativity has withstood many experimental tests, alternative theories of gravity have been proposed to explain the discrepancies between General Relativity and observations of the universe. Modified Gravity is a theory that suggests that gravity behaves differently on large scales than it does on small scales, which could account for some of these discrepancies. \n\nDark Matter is another theory which proposes that there exists an invisible form of matter in the universe which interacts with normal matter only through its gravitational pull. This would explain why galaxies rotate faster than expected based on their visible mass alone.\n\n ![Graph](image://143ba739-4e2e-43f4-9c91-024057de437c \"Dark matter\")\n\nRecent studies suggest that dark matter could make up around 27% of the universe, outnumbering ordinary matter by a factor of 6 to 1. \n\nThe existence of dark matter has been inferred by observing its gravitational effects such as bending light from distant colliding galaxies. While alternative theories are still being explored, they provide exciting new insights into our understanding of gravity and how it affects our universe.\n\n","60e1bc9c-75c4-42f7-830e-7263f7842817",[779],{"id":780,"data":781,"type":51,"version":25,"maxContentLevel":28},"b0c3417f-e269-4c17-8ad0-034d726f0c9f",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":782,"binaryCorrect":784,"binaryIncorrect":786},[783],"What percentage of the universe is made up of dark matter?",[785],"27%",[787],"6%",{"id":789,"data":790,"type":25,"maxContentLevel":28,"version":25,"reviews":794},"7e759ee4-292c-474a-a29c-e88c4698c44b",{"type":25,"title":791,"markdownContent":792,"audioMediaId":793},"Philosophical Implications of Relativity","The Theory of Relativity has had profound implications for our understanding of the nature of time, space, and reality. It suggests that time is not absolute but relative to an observer's motion; two observers in different frames of reference can experience different rates of time passing. \n\nSimilarly, space is no longer a fixed three-dimensional grid but rather a four-dimensional continuum known as spacetime where objects move along curved paths due to gravity or acceleration.\n\n ![Graph](image://b7c35d14-0c75-4040-94d5-942e243d349d \"Plato\")\n\nThese ideas echo concepts which have been explored in philosophy since ancient times. Thinkers such as Aristotle proposed that time was an illusion created by the human mind and Plato suggested that physical objects were merely shadows cast on a higher dimensional realm. \n\nThe Theory of Relativity provides a scientific counterpart to these philosophical ideas and offers new insights into how we perceive reality. \n\nFor example, it suggests that what we consider 'the present' is actually just a momentary snapshot from our own frame of reference; all moments exist simultaneously in spacetime regardless if they are perceived or not. \n\nThese revelations challenge us to reconsider our perception of the universe and open up exciting possibilities for further exploration into its mysteries.\n\n","9ea005be-bc87-4b57-97c5-55ca953b76bb",[795],{"id":796,"data":797,"type":51,"version":25,"maxContentLevel":28},"a8afde67-0003-4470-bdb6-a7969be83039",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":798,"binaryCorrect":800,"binaryIncorrect":802},[799],"What does the Theory of Relativity suggest about the nature of time?",[801],"Time is not absolute but relative to an observer's motion",[803],"Time is an illusion created by the human mind",{"id":805,"data":806,"type":27,"maxContentLevel":28,"version":25,"orbs":809},"b781dc5a-3fc1-4aa3-8fe9-4eef6b1b407e",{"type":27,"title":807,"tagline":808},"Waves and Sound","How waves transmit energy across space.",[810,881],{"id":811,"data":812,"type":21,"version":25,"maxContentLevel":28,"pages":814},"e3a06498-7077-446b-b72f-dac9dd8edbed",{"type":21,"title":813},"Understanding Waves",[815,831,849,865],{"id":816,"data":817,"type":25,"maxContentLevel":28,"version":25,"reviews":821},"72cbfb23-d4fb-4b76-8d86-5d22f7a7cc6a",{"type":25,"title":818,"markdownContent":819,"audioMediaId":820},"What are waves","Waves are a fundamental concept in physics, and can be defined as the transfer of energy through a medium without any net movement of matter. Waves come in many forms, such as sound waves, light waves, and water waves. Sound is an example of a mechanical wave that requires a medium to travel through; it is created by vibrating objects which cause air molecules to vibrate back and forth creating pressure variations that propagate outward from the source. \n\n ![Graph](image://d7d78a53-09a3-4379-8cd0-ab2a7838f386 \"Sound waves\")\n\nLight on the other hand is an electromagnetic wave that does not require a medium for propagation; it travels at about 300 million meters per second in vacuum! Water waves are also mechanical waves caused by disturbances on the surface of water bodies like oceans or ponds. These ripples spread outwards from their point of origin as the energy from the disturbance moves through the water - this phenomenon has been observed since ancient times with Aristotle noting how circular ripples form when stones were thrown into still pools.\n\n","5bfba6ea-d621-4c58-9e9a-ff4f7292ad37",[822],{"id":823,"data":824,"type":51,"version":25,"maxContentLevel":28},"47adf53f-3c02-4b8a-bd63-3fcc80ad55d9",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":825,"binaryCorrect":827,"binaryIncorrect":829},[826],"Who noted the phenomenon of water waves in ancient times?",[828],"Aristotle",[830],"Plato",{"id":832,"data":833,"type":25,"maxContentLevel":28,"version":25,"reviews":837},"5ca6d69e-33bc-4c55-8236-b80e7beacbe2",{"type":25,"title":834,"markdownContent":835,"audioMediaId":836},"Types of waves","Waves come in two main types: transverse and longitudinal. Transverse waves are characterized by particles that move perpendicular to the direction of wave travel, while longitudinal waves have particles that move parallel to the direction of wave travel. Examples of transverse waves include light, water ripples, and seismic S-waves; examples of longitudinal waves include sound and seismic P-waves.\n\n ![Graph](image://87a5df1f-186c-4795-8d96-4bb10d5700bb \"Water ripples\")\n\nMechanical waves require a medium for transmission such as air or water, whereas electromagnetic waves do not need a medium for transmission - they can travel through vacuum! This is why we can see stars millions of light years away despite there being no physical connection between us and them. \n\nMechanical waves transfer energy from one point to another via particle movement within the medium itself, while electromagnetic radiation transfers energy through electric and magnetic fields which oscillate at right angles to each other as well as in the direction of wave propagation.\n\n","d7bc07e6-f233-4f84-b347-30de46063827",[838],{"id":839,"data":840,"type":51,"version":25,"maxContentLevel":28},"921685e8-3313-4cc4-9758-2144edcae786",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":841,"multiChoiceCorrect":843,"multiChoiceIncorrect":845},[842],"What are two types of waves?",[844],"Transverse and longitudinal",[846,847,848],"Transverse and seismic","Longitudinal and seismic","Light and sound",{"id":850,"data":851,"type":25,"maxContentLevel":28,"version":25,"reviews":855},"d4458122-8d2c-4a49-bd3e-0b3f9e9d2902",{"type":25,"title":852,"markdownContent":853,"audioMediaId":854},"Properties of waves","The properties of waves are used to characterize them and describe their behaviour. The highest point a wave reaches is called its crest and the low point of the cycle is called a trough. Amplitude is the maximum displacement from equilibrium, or the height of a wave crest above its resting position. Wavelength is the distance between two successive crests or troughs, while frequency is the number of complete cycles per unit time - usually measured in Hertz (Hz). Wave speed is determined by multiplying wavelength by frequency; it describes how quickly a wave moves through space and can be expressed as meters per second (m/s).\n\n ![Graph](image://452c77f6-4422-40ab-9088-e806f852f95a \"Wavelength\")\n\nThe properties of waves are related to one another. Higher amplitude waves have greater energy and higher frequencies correspond to shorter wavelengths. For example, sound travels at 343 m/s in air regardless of its frequency but lower-frequency sounds will have longer wavelengths than higher-frequency sounds.\n\n","63baa6c4-c9b0-4530-9128-fe302bafbc7a",[856],{"id":857,"data":858,"type":51,"version":25,"maxContentLevel":28},"70e7fa01-b176-4437-9a17-f25934e0fe89",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":859,"binaryCorrect":861,"binaryIncorrect":863},[860],"What is the term used to describe the maximum displacement from equilibrium of a wave?",[862],"Amplitude",[864],"Wavelength",{"id":866,"data":867,"type":25,"maxContentLevel":28,"version":25,"reviews":871},"a2f44338-ed95-4aa1-ba87-057a3ffa42c7",{"type":25,"title":868,"markdownContent":869,"audioMediaId":870},"Wave behavior","Waves exhibit a variety of characteristic behaviors, including refraction, reflection, interference and diffraction. Refraction is the bending of waves when they pass from one medium to another. For example, light bends when it passes through water or glass. Reflection occurs when a wave bounces off an obstacle and returns in the opposite direction; this can be seen in the reflection of light by a mirror. Interference is the combination of two or more waves that results in either constructive interference (amplification) or destructive interference (cancellation). Diffraction is the spreading out of waves around obstacles; this can be observed at sea where waves bend around islands and other objects.\n\n ![Graph](image://b170c912-8258-4534-b720-28581c7e1865 \"Refraction of light\")\n\nThese behaviors can all interact with each other: refracted rays will interfere with reflected ones, while diffracted rays may constructively interfere with each other if their wavelengths match up correctly. For instance, if you observe ocean swells near a rocky shoreline you'll see how these different effects combine together - some swells will be bent by refraction as they approach land while others will bounce back due to reflection before being spread out by diffraction into smaller ripples which then interact with each other via interference!\n\n","c4395971-975f-4688-b3a1-c3138f680f4a",[872],{"id":873,"data":874,"type":51,"version":25,"maxContentLevel":28},"dadc2e24-a5ed-4735-8c80-e2fdc5bdb790",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":875,"binaryCorrect":877,"binaryIncorrect":879},[876],"What is the term used to describe the combination of two or more waves resulting in amplification or cancellation?",[878],"Interference",[880],"Refraction",{"id":882,"data":883,"type":21,"version":25,"maxContentLevel":28,"pages":885},"05a96f1a-b5be-49e0-8549-b128bb1bff95",{"type":21,"title":884},"Sound and Its Properties",[886,901,919,937,955,973],{"id":887,"data":888,"type":25,"maxContentLevel":28,"version":25,"reviews":892},"9c68670c-8d80-43b4-94bd-596a4405c59a",{"type":25,"title":889,"markdownContent":890,"audioMediaId":891},"Sound waves"," ![Graph](image://b649e97b-0db5-43fa-bb09-da18d5b14c58 \"A canyon\")\n\nSound waves are longitudinal waves that travel through a medium, such as air or water. They are created by the vibrations of objects and usually travel outward in all directions from the source. The amplitude of sound waves determines how loud they will be perceived; higher amplitudes create louder sounds while lower amplitudes create softer ones. Frequency is also important: low frequencies produce deep bass tones while high frequencies produce shrill treble notes.\n\nThe speed of sound varies depending on the material it travels through; for example, sound moves faster in solids than liquids and gases due to their differing levels of stiffness. In dry air at sea level, sound travels at approximately 343 meters per second (1125 feet/second). \n\nThis means that if you shout across a canyon 1 kilometer wide (0.62 miles), your voice would take about 3 seconds to reach the other side. Sound can also travel through walls and other solid materials because its energy is transferred via vibrations between particles within them - this phenomenon is known as 'structure-borne' transmission and explains why footsteps coming from floors above us can sound so loud.\n\n","0d141b55-3007-477b-91bb-2b9cbc0e0647",[893],{"id":894,"data":895,"type":51,"version":25,"maxContentLevel":28},"05be21df-510e-41e9-a174-9de8d6cbc42a",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":896,"binaryCorrect":898,"binaryIncorrect":899},[897],"What determines how loud a sound wave will be perceived?",[862],[900],"Frequency",{"id":902,"data":903,"type":25,"maxContentLevel":28,"version":25,"reviews":907},"d58d482e-0240-4798-8f5f-1d9b5119a2d8",{"type":25,"title":904,"markdownContent":905,"audioMediaId":906},"The speed of sound","The speed of sound is the rate at which a sound wave propagates through a medium, and it varies depending on the properties of that medium. In dry air at sea level, sound travels at approximately 343 meters per second (1125 feet/second). \n\nThis speed can be affected by several factors such as temperature, humidity, and pressure. The inertial properties of a medium determine how quickly it responds to changes in pressure; for example, solids are more rigid than liquids or gases so they tend to have higher speeds of sound. Elasticity also plays an important role: materials with greater elasticity will absorb energy from waves more easily and thus reduce their speed.\n\n ![Graph](image://a050c264-875e-490c-b6ed-ca357134a913 \"A bass guitarist makes some noise\")\n\nHigher temperatures tend to increase the speed of sound - as temperatures increase, the molecules in air move faster and collide more often resulting in faster propagation speeds. Similarly, high levels of humidity decrease the density of air, which allows sound waves to travel faster.These effects are unlikely to be significant in everyday life but they can make all the difference when recording audio accurately or measuring distances using sonar technology!\n\n","b771a23a-4ee3-4986-9396-4520676fd684",[908],{"id":909,"data":910,"type":51,"version":25,"maxContentLevel":28},"d263927f-9062-4d18-8b1b-25c6a6d67f01",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":911,"multiChoiceCorrect":913,"multiChoiceIncorrect":915},[912],"How does an increase in temperature affect the speed of sound?",[914],"It increases it",[916,917,918],"It decreases it","It has no effect","It makes it louder",{"id":920,"data":921,"type":25,"maxContentLevel":28,"version":25,"reviews":925},"408bfbc3-5d44-48ea-a532-4c21ece096ca",{"type":25,"title":922,"markdownContent":923,"audioMediaId":924},"Intensity and decibels","Sound intensity is the amount of power carried by a sound wave per a unit of area. It is often measured in decibels (dB). The human ear can comfortably detect sounds ranging from 0 dB to 130dB. It can certainly hear sounds that exceed 130dB, but at those volumes and above it will be damaged. \n\nFor comparison, breathing is typically 10 dB, a whisper is around 30-40 dB, normal conversation ranges from 60-70 dB, while a rock concert or nightclub can reach up to 120 dB. A gunshot registers at approximately 140 dB - loud enough to cause permanent hearing damage. Sounds above 130 dB exceed the ‘pain threshold’ and are painful to hear. \n\n ![Graph](image://f3ba05bb-4ee1-46dc-994e-24b7624c6ef1 \"A rock concert\")\n\nDecibel levels are logarithmic rather than linear. This means that an increase of 10 decibels represents a tenfold increase in sound intensity. For example, 40dB would be perceived as ten times as loud as 30dB.\n\nThis makes it easier for us to compare a wide range of different sounds on the same scale. It also helps us understand why prolonged exposure above certain levels of decibels can lead to hearing loss: even small increases in the level of decibels can have drastic effects on our ears!\n\n","8e2f2365-149f-4608-b3c3-f3e84366fb71",[926],{"id":927,"data":928,"type":51,"version":25,"maxContentLevel":28},"d81604d1-b2b5-456c-a987-a9a4aeff7959",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":929,"multiChoiceCorrect":931,"multiChoiceIncorrect":933},[930],"How is sound intensity measured?",[932],"Decibels (dB)",[934,935,936],"Hertz (Hz)","Kilograms (kg)","Meters (m)",{"id":938,"data":939,"type":25,"maxContentLevel":28,"version":25,"reviews":943},"1c771581-7e67-4fb5-bd18-f46da8e42bba",{"type":25,"title":940,"markdownContent":941,"audioMediaId":942},"Doppler effect","\n ![Graph](image://63540b6b-22e2-400c-bd7d-86625f1e22d1 \"An illustration of the Doppler Effect\")\n\nThe Doppler effect is a phenomenon that occurs when waves, such as sound or light, are emitted from a source that is moving relative to an observer. As the source moves closer to an observer, the frequency of the wave increases; conversely, as it moves away from them, the frequency decreases. \n\nThis principle applies to sound waves and the change in frequency can be heard as a shift in pitch. As an object such as an ambulance approaches us at high speed, we hear its siren with increased pitch due to the Doppler effect. Similarly, when it passes us and continues on its way into the distance, we hear its siren with decreased pitch. The magnitude of this shift depends on both how fast the object is travelling relative to us and how quickly our ears can detect changes in frequency\n\n\nInterestingly enough, this same concept also applies to electromagnetic waves beyond Earth's atmosphere: stars emit light waves which experience similar shifts depending on their motion relative to observers here on Earth. Astronomers use these shifts in wavelength known as redshifts or blueshifts respectively to observe the movement of distant objects in space.\n","c0f69c11-6b1f-4136-aa54-5c72f1242dcf",[944],{"id":945,"data":946,"type":51,"version":25,"maxContentLevel":28},"b961df41-3074-41c6-bcd8-7bbb2d41ea51",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":947,"multiChoiceCorrect":949,"multiChoiceIncorrect":951},[948],"What phenomenon causes a shift in pitch when an object such as an ambulance approaches or moves away from an observer?",[950],"The Doppler effect",[952,953,954],"The Reflection effect","The Refraction effect","The Resonance effect",{"id":956,"data":957,"type":25,"maxContentLevel":28,"version":25,"reviews":961},"05edcfe6-60b7-4fad-bc39-06ec10e41f3f",{"type":25,"title":958,"markdownContent":959,"audioMediaId":960},"Resonance","Resonance is an important concept in the study of sound waves. It occurs when a vibrating object causes another object or system to vibrate at the same frequency. This phenomenon amplifies and reinforces certain frequencies, resulting in louder sounds with greater clarity and depth.\n\n ![Graph](image://976254df-0e16-4a3c-a81c-2117459309d2 \"A guitar\")\n\nResonance is harnessed by many musical instruments in producing their characteristic sounds. For example, blowing into the mouthpiece of a brass instrument such as a trumpet results in resonance and produces vibrations in a column of air contained within the instrument’s metal tube. \n\nA loud and hopefully pleasant sound is produced. Similarly, blowing into the reed on a woodwind instrument like a saxaophone creates resonance vibrations in an air column and a corresponding musical sound. \n\nThe resonance of musical instruments plays an important role in their unique timbre - that is, their characteristic tone quality. Resonance also affects how loud different notes are played on each instrument: some notes will be naturally louder than others due to resonant properties within the instrument's design!\n\n","f2efc1b0-256a-496b-9a22-af0f03211e72",[962],{"id":963,"data":964,"type":51,"version":25,"maxContentLevel":28},"91b7afaa-c1d7-43db-8b29-df3739c69a45",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":965,"multiChoiceCorrect":967,"multiChoiceIncorrect":969},[966],"How does resonance affect the sound of musical instruments?",[968],"It affects the timbre and volume of different notes",[970,971,972],"It affects the speed of sound waves","It affects the pitch of the notes","It affects the volume of the notes",{"id":974,"data":975,"type":25,"maxContentLevel":28,"version":25,"reviews":979},"f25cc134-1f63-4a35-b6e0-d0d31b29c425",{"type":25,"title":976,"markdownContent":977,"audioMediaId":978},"Ultrasonic waves","Ultrasonic waves are sound waves with frequencies higher than the upper limit of human hearing, which is typically around 20 kHz for healthy young humans. These high-frequency sound waves have a wide range of applications in both medical and industrial settings.\n\nIn medicine, ultrasonic imaging is used to create detailed images of organs and tissues inside the body without using radiation or invasive procedures. Ultrasound can also be used to detect blood flow abnormalities, measure fetal heart rate during pregnancy, and even break up kidney stones. In industry, ultrasonic cleaning uses high frequency sound waves to remove dirt from delicate parts that would otherwise be difficult or impossible to clean manually. It has been found to be more effective than traditional methods such as scrubbing or chemical solvents.\n\nUltrasonics can also be used for non-destructive testing (NDT) - a process where materials are tested for flaws without damaging them in any way. This technique is commonly employed in aerospace engineering and automotive manufacturing industries where safety is paramount; it allows engineers to identify potential problems before they become serious issues down the line!\n","f05f1031-512c-455c-a86a-d00e4965196c",[980],{"id":981,"data":982,"type":51,"version":25,"maxContentLevel":28},"e32e2ec8-7725-4b44-96d7-fc5c47ae851a",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":983,"multiChoiceCorrect":985,"multiChoiceIncorrect":987},[984],"What is the upper limit of human hearing for most healthy young humans?",[986],"20 kHz",[988,989,990],"10 kHz","30 kHz","40 kHz",{"id":992,"data":993,"type":27,"maxContentLevel":28,"version":25,"orbs":996},"061a0d1c-b23d-466f-9ea1-c6eef51d1e8d",{"type":27,"title":994,"tagline":995},"Light and Optics","Keeping things light.",[997,1052,1099],{"id":998,"data":999,"type":21,"version":25,"maxContentLevel":28,"pages":1001},"4abdccc3-9bbb-4ce2-894e-39124d98ac01",{"type":21,"title":1000},"Fundamentals of Light",[1002,1018,1034],{"id":1003,"data":1004,"type":25,"maxContentLevel":28,"version":25,"reviews":1008},"7ca0d416-6057-44fe-8fc2-8acb8b45772c",{"type":25,"title":1005,"markdownContent":1006,"audioMediaId":1007},"The nature of light","Light is a form of energy that can be seen by the human eye. It is part of the electromagnetic spectrum, which includes radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. \n\nLight has both wave-like and particle-like properties. It can behave either as a wave or as particles called photons, depending on the circumstances. Photons are massless particles that carry energy in discrete packets proportional to their frequency and wavelength.\n\n ![Graph](image://92e666e0-4c9a-4ae0-b1e4-b9a3728905a3 \"An x-ray.\")\n\nThe visible portion of the electromagnetic spectrum consists of wavelengths between 400 nanometers (violet) and 700 nanometers (red). This range corresponds to frequencies between 800 terahertz (THz) and 400THz - The human eye is sensitive enough to detect single photons within this range. Our perception of color depends on the energy levels of photons reaching our eyes, and the wavelengths they correspond to. The light that we perceive as white contains multiple frequencies across the entire visible spectrum.\n\n","ef6e553b-0d3f-41a0-9217-c85051b3e999",[1009],{"id":1010,"data":1011,"type":51,"version":25,"maxContentLevel":28},"bd3a487a-3c90-4063-8a5c-5cfc9e9f80bc",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1012,"binaryCorrect":1014,"binaryIncorrect":1016},[1013],"What are the particles that carry energy in discrete packets proportional to their frequency and wavelength?",[1015],"Photons",[1017],"Electrons",{"id":1019,"data":1020,"type":25,"maxContentLevel":28,"version":25,"reviews":1024},"939ef532-609c-4410-994a-85024c914106",{"type":25,"title":1021,"markdownContent":1022,"audioMediaId":1023},"Properties of light","Light is a wave, and as such it has certain properties that are unique to waves - including amplitude, wavelength, frequency and speed. Unlike mechanical waves, light waves can travel in a vacuum. The speed of light in a vacuum is one of the most fundamental constants in nature. As far as we know, nothing can travel faster than the speed of light: which travels in a vacuum at 299 792 458 meters per second. This means that light travels around the world seven times per second!\n\n ![Graph](image://6e58365d-12dd-4344-b111-01625fa5a57e \"Someone wearing sunglasses\")\n\nThe amount of electromagnetic power radiated by an object is described as its luminosity. The luminous intensity of light is the quantity of light emitted per unit time and per unit solid angle - essentially this measures the light received from a source within a particular area. Light also has a propagation direction which determines where it will travel when emitted from a source.\n\n","b2006ce1-fe58-49f5-bc1a-3bb707704d12",[1025],{"id":1026,"data":1027,"type":51,"version":25,"maxContentLevel":28},"1a7daead-f1ab-4918-8afb-c4fa1d093d11",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1028,"binaryCorrect":1030,"binaryIncorrect":1032},[1029],"What term is used to describe the amount of electromagnetic power radiated by an object?",[1031],"Luminosity",[1033],"Magnetism",{"id":1035,"data":1036,"type":25,"maxContentLevel":28,"version":25,"reviews":1040},"5152aaed-3c23-42e8-8900-fbd253ced40d",{"type":25,"title":1037,"markdownContent":1038,"audioMediaId":1039},"Reflection of light","Reflection of light is the bouncing back of light rays when they hit a surface. The angle at which the approaching light ray hits the reflecting surface is known as the angle of incidence, and this determines how much of the light will be reflected. The angle between the reflected ray and a line perpendicular to the reflecting surface (known as normal) is called angle of reflection.\n\nSpecular reflection occurs when all incident rays are reflected in one direction, creating an image that appears to come from a single point source - like a mirror or polished metal surfaces. Diffuse reflection occurs when incident rays are scattered in many directions, resulting in no clear image being formed - like on matte surfaces such as paper or cloth.\n\nLight reflects off objects differently depending on their texture; for example, smooth surfaces reflect more than rough ones due to less scattering occurring at each point along its path. Additionally, certain materials have special properties that allow them to selectively absorb certain wavelengths while reflecting others – these materials are used in optical filters for cameras and telescopes alike.\n\n ![Graph](image://83072fc2-5e51-46f8-8b0d-8cffbc812302 \" a reflection bouncing off a smooth surface\")","a76db17c-240e-41c0-99d4-8a8cd164d693",[1041],{"id":1042,"data":1043,"type":51,"version":25,"maxContentLevel":28},"2a65caf9-8dcd-40a0-9ce3-5d006001e49f",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1044,"multiChoiceCorrect":1046,"multiChoiceIncorrect":1048},[1045],"What is the result of light reflecting off of a smooth surface compared to a rough one?",[1047],"Less scattering",[1049,1050,1051],"More scattering","More absorption","Less absorption",{"id":1053,"data":1054,"type":21,"version":25,"maxContentLevel":28,"pages":1056},"34ace2bb-0b93-48ad-86c2-f30901fe67b4",{"type":21,"title":1055},"Light Behavior",[1057,1075,1081],{"id":1058,"data":1059,"type":25,"maxContentLevel":28,"version":25,"reviews":1063},"df4a684f-f15e-4998-b539-a1cd2614ba17",{"type":25,"title":1060,"markdownContent":1061,"audioMediaId":1062},"Refraction of light","Refraction of light is the bending of light as it passes from one medium to another, such as air to water. The angle at which the incident ray enters a new medium is known as the angle of incidence, and this determines how much refraction will occur. The angle between the refracted ray and a line perpendicular to the surface (known as normal) is called angle of refraction. Refractive index measures how much a material bends light; different materials have different indexes, with glass having an index around 1.5 times that of air.\n\nLight refraction can be seen in everyday life - rainbows are created when sunlight passes through raindrops and gets bent by their curved surfaces, while magnifying glasses use lenses to bend incoming rays so they converge on a single point for magnification purposes. The power of refraction is also used in eyeglasses to correct vision.\n\n ![Graph](image://961df3c0-da92-4b2f-9985-47e70ee2ff9e \" a rainbow present through rain\")","607f1b04-7f3a-454b-897c-2aa0277e69fc",[1064],{"id":1065,"data":1066,"type":51,"version":25,"maxContentLevel":28},"379c3d22-b0f9-4a79-a8c4-a6433bd592fb",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1067,"multiChoiceCorrect":1069,"multiChoiceIncorrect":1071},[1068],"What is the angle between the refracted ray and a line perpendicular to the surface known as?",[1070],"Angle of refraction",[1072,1073,1074],"Angle of incidence","Refractive index","Normal",{"id":1076,"data":1077,"type":25,"maxContentLevel":28,"version":25},"43b9dd81-f470-4bdc-8f65-acfe1ea463e7",{"type":25,"title":1078,"markdownContent":1079,"audioMediaId":1080},"Lenses and mirrors","Lenses and mirrors are two of the most important tools in optics, allowing us to manipulate light for a variety of purposes. Lenses are curved pieces of glass or plastic that bend incoming light rays, while mirrors are surfaces that reflect them. Flat lenses have no curvature and do not usually refract light. \n\nConvex lenses curve outward and cause parallel rays to converge at a single point known as the focal point. Concave lenses curve inward and cause diverging rays to meet at the focal point. Mirrors can also be either flat or curved – concave mirrors focus incident light onto one spot , while convex mirrors spread out reflected light over a larger area.\n\n\n ![Graph](image://8c12a609-497b-45a4-b243-e995692622ad \"A concave lense\")\n\nThese objects have many practical applications - telescopes use both lenses and mirrors to magnify distant objects; corrective eyeglasses use concave lenses to correct nearsightedness and convex lenses to correct farsightedness; microscopes use convex lenses for magnification; concave mirrors are used to focus laser beams; even our car headlights make use of parabolic reflectors! The possibilities with these tools seem endless – from helping us explore space more deeply than ever before, to aiding us in everyday life tasks such as driving safely at night!","7f3733a0-3f47-4e1e-90c1-d6aeebc46563",{"id":1082,"data":1083,"type":25,"maxContentLevel":28,"version":25,"reviews":1087},"fe1dd9ae-96cc-4d75-b272-6c606ba74eb5",{"type":25,"title":1084,"markdownContent":1085,"audioMediaId":1086},"The human eye","The human eye is an incredible organ, capable of processing visible light and allowing us to see the world around us. Light enters through the cornea, a transparent outer layer that helps focus incoming rays. The pupil acts as an aperture for light, and its size is adjusted by a muscle in the coloured iris to control how much light enters the eye. Once inside, light passes through a lens which further refracts it and focuses it onto the retina at the back of our eyes. Here, photoreceptors convert incoming light into electrical signals which are then sent to our brain via an optic nerve.\n\nAt this point in its journey, light has been focused onto one spot known as the focal point. This process allows us to distinguish between different colors and shades; each type of photoreceptor responds differently to different wavelengths of visible light – red-sensing cones detect red hues while blue-sensing cones detect blues and green-sensing cones detect greens! Amazingly enough, we can perceive up to a million distinct colors thanks to these specialized cells!\n\n ![Graph](image://0be575a8-336b-4e5d-b903-c6ea044fbd0a \"a close up of an eye\")","867b6c62-95b7-4efa-9cee-8370e66e25f2",[1088],{"id":1089,"data":1090,"type":51,"version":25,"maxContentLevel":28},"d8c20af2-b6b6-4198-9bac-c29c8d8a17a8",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1091,"multiChoiceCorrect":1093,"multiChoiceIncorrect":1095},[1092],"What part of the eye helps to control how much light enters the eye?",[1094],"The iris",[1096,1097,1098],"The lens","The cornea","The pupil",{"id":1100,"data":1101,"type":21,"version":25,"maxContentLevel":28,"pages":1103},"9bb3fe6c-281c-43c4-b34c-d16e2700c200",{"type":21,"title":1102},"Light and Color",[1104,1119,1133,1148],{"id":1105,"data":1106,"type":25,"maxContentLevel":28,"version":25,"reviews":1110},"8d28e40c-74ef-4a56-aa43-b1ecfd681892",{"type":25,"title":1107,"markdownContent":1108,"audioMediaId":1109},"Color and light","The visible spectrum of light is composed of a range of different colors, each with its own unique wavelength. When white light passes through a prism, it is split into these individual colors – red has the longest wavelength and violet has the shortest. This phenomenon can be explained by refraction; when light enters a medium at an angle, it bends inwards due to the change in speed caused by the new material's density. The amount of bending depends on the angle and color of incoming rays; shorter wavelengths bend more than longer ones, resulting in their separation into distinct bands!\n\nObjects appear colored because they absorb some wavelengths while reflecting others back towards our eyes. For example, grass appears green because it absorbs all other colors except for green which is reflected back to us. Similarly, blue objects absorb all but blue wavelengths and reflect them instead – this explains why we see them as blue!\n\n ![Graph](image://e9141ec5-1a2b-4b53-8c27-293c1b939a7a \"the visible spectrum of light\")","d8a242aa-74ec-4f79-adbc-8888bd7d910b",[1111],{"id":1112,"data":1113,"type":51,"version":25,"maxContentLevel":28},"eb8e0217-99b8-4609-9c48-486b8efef64f",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1114,"binaryCorrect":1116,"binaryIncorrect":1117},[1115],"What phenomenon explains why white light is split into different colors when passed through a prism?",[880],[1118],"Reflection",{"id":1120,"data":1121,"type":25,"maxContentLevel":28,"version":25,"reviews":1125},"5726d53d-6b2d-4296-9c4b-9bb4ea58d6b3",{"type":25,"title":1122,"markdownContent":1123,"audioMediaId":1124},"Interference and diffraction","Interference is the phenomenon of two or more waves overlapping and combining to form a new wave. When two waves are in phase, they combine constructively, resulting in an amplified wave with greater amplitude than either of the original waves. \n\nThis is known as constructive interference. Conversely, when two waves are out of phase they will cancel each other out and create a wave with lower amplitude than either of the originals; this is called destructive interference. Interference can be observed in many areas such as soundwaves bouncing off walls or light reflecting off surfaces like mirrors and lenses.\n\n ![Graph](image://f3a3887d-e2d8-4ebb-8b67-629d0892fb76 \"Diffraction\")\n\nDiffraction occurs when light passes through small openings or around obstacles that are comparable to its wavelength size – it bends around them instead of passing straight through! \n\nThis bending effect causes light to spread out from its source, creating patterns on nearby surfaces such as sunlight tracing along the edge of a cloud. \n\nDiffraction also affects how we perceive objects; if an object is smaller than half the wavelength of visible light then it is impossible to see clearly, even with the most powerful microscope, due to diffraction effects. This is known as the diffraction barrier.\n\n","dedcd7d1-a461-4f69-84d4-88fa7f777444",[1126],{"id":1127,"data":1128,"type":51,"version":25,"maxContentLevel":28},"a0bd5bdb-720e-420e-9d61-251b949e4bd2",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1129,"binaryCorrect":1131,"binaryIncorrect":1132},[1130],"What phenomenon occurs when two waves overlap and combine to form a new wave?",[878],[1118],{"id":1134,"data":1135,"type":25,"maxContentLevel":28,"version":25,"reviews":1139},"0175ce90-860e-40e3-a5f9-ff12ca7fc63b",{"type":25,"title":1136,"markdownContent":1137,"audioMediaId":1138},"Polarization","Polarization is the process of orienting light waves in a single direction. Unpolarized light consists of many different directions, while polarized light has all its waves aligned in one plane. This can be achieved by passing unpolarized light through a polarizing filter which only allows vibrations at a certain angle to pass through, resulting in polarized light. \n\n ![Graph](image://d708c8d6-c7c6-4c9b-ba94-1cedba91ba48 \"A circular dichroism spectrometer. Image: Kaidor, CC BY-SA 3.0, via Wikimedia Commons\")\n\nPolarization is used for various applications such as reducing glare from surfaces like water or snow and improving visibility when driving on sunny days with polarized sunglasses. It also plays an important role in communication systems where it helps reduce interference from other signals and improves signal strength. \n\nAdditionally, polarization can be used to study the way certain molecules are orientated within systems. This technique is known as circular dichroism spectroscopy and is widely used in biochemistry research - particularly in studying the structure of proteins.\n\n","d6399270-f5d1-4105-8533-c4abd62ff058",[1140],{"id":1141,"data":1142,"type":51,"version":25,"maxContentLevel":28},"d549cec6-1974-48d1-acb4-48ad081a91a3",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1143,"multiChoiceCorrect":1145,"multiChoiceIncorrect":1147},[1144],"What technique is used to study the way certain molecules are orientated within systems?",[1146],"Circular dichroism spectroscopy",[994,1136,880],{"id":1149,"data":1150,"type":25,"maxContentLevel":28,"version":25,"reviews":1154},"ac63178f-5c6d-456a-af22-fb5eedb6678b",{"type":25,"title":1151,"markdownContent":1152,"audioMediaId":1153},"Spectra","Spectra are the unique fingerprints of light sources, and can be used to identify them. Spectrometers measure spectra by splitting light into its component wavelengths, allowing us to analyze the light source or how it interacts with a sample. This is done using a prism or diffraction grating which separates different colors in the visible spectrum, as well as other types of radiation such as infrared and ultraviolet. By measuring how much energy is present at each wavelength we can create an emission or absorption spectrum that reveals information about the source's temperature, chemical composition and motion.\n\nFor example, astronomers use spectroscopy to study stars by analyzing their spectral lines - dark lines in a star's spectrum indicate elements like hydrogen or helium that are present in its atmosphere. Similarly, chemists use spectrometers to identify unknown substances based on their characteristic absorption patterns.\n\n","c5394d17-c987-4b31-be20-1fd7acb2580c",[1155],{"id":1156,"data":1157,"type":51,"version":25,"maxContentLevel":28},"6dc40861-7b7f-42a8-aa7f-a05dc52a9fbc",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1158,"binaryCorrect":1160,"binaryIncorrect":1162},[1159],"What device is used to measure spectra by splitting light into its component wavelengths?",[1161],"Spectrometer",[1163],"Prism",{"id":1165,"data":1166,"type":27,"maxContentLevel":28,"version":25,"orbs":1169},"8a3908c3-f6a3-496e-af57-0d8925ebe49a",{"type":27,"title":1167,"tagline":1168},"Electricity and Magnetism","The interrelated forces that govern electronics and magnetics.",[1170,1258,1312],{"id":1171,"data":1172,"type":21,"version":25,"maxContentLevel":28,"pages":1174},"6e53663b-1e6a-4dbf-a156-9769f60138a5",{"type":21,"title":1173},"Fundamentals of Electric Charge",[1175,1190,1208,1226,1242],{"id":1176,"data":1177,"type":25,"maxContentLevel":28,"version":25,"reviews":1181},"1a2b217e-dec1-4ec3-9a5e-684a860152a3",{"type":25,"title":1178,"markdownContent":1179,"audioMediaId":1180},"Electric charge","Electric charge is a fundamental property of matter that describes the interaction between particles and electromagnetic fields. It is measured in coulombs (C): a coulomb is roughly equal to the amount of electric charge carried by 6.24 x 10¹⁸ electrons. Objects can have either a positive or negative electric charge, depending on whether they contain more protons than electrons (positive) or vice versa (negative). Protons carry a positive electrical charge, while neutrons are neutral and do not carry any electrical charge at all.\n\n ![Graph](image://651db602-f9c8-422f-9fc1-b64bb103933a \"A Van de Graaff generator. Image: Zátonyi Sándor, (ifj.) Fizped, CC BY 3.0, via Wikimedia Commons\")\n\nOpposite charges attract each other due to their electrostatic force, while like charges repel one another as they push away from each other with an equal but opposite force. This phenomenon explains why lightning occurs when clouds become charged with static electricity - the negative charges at the bottom of the cloud are attracted to positive charges on Earth's surface below it until there is enough energy for them to discharge into a lightning bolt! The same principle applies to magnets; two north poles will repel each other, while two south poles will also repel each other - only when you bring together opposite poles will they be attracted towards one another.\n\n","830dc5cb-b3ff-4414-9b5b-b8a6324cc9f4",[1182],{"id":1183,"data":1184,"type":51,"version":25,"maxContentLevel":28},"dbb052a5-d5ad-4e4a-89e6-81a47400899e",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1185,"multiChoiceCorrect":1187,"multiChoiceIncorrect":1189},[1186],"What is the unit of measurement for electric charge?",[1188],"Coulombs (C)",[575,573,571],{"id":1191,"data":1192,"type":25,"maxContentLevel":28,"version":25,"reviews":1196},"2cd230c4-e7f7-4444-a9d8-4eb5bdf3edea",{"type":25,"title":1193,"markdownContent":1194,"audioMediaId":1195},"Electric current","Electric current is the flow of electric charge through a material, and it is measured in amperes (A). Direct current (DC) flows in one direction only, while alternating current (AC) reverses its direction periodically. DC is used in batteries to power most electronic devices such as computers and phones, while AC is used in household electricity and powers larger appliances like washing machines and refrigerators.\n\nThe difference between direct and alternating currents can be seen when looking at voltage or current plotted against time- DC has a flat line with no variation over time, whereas AC has an oscillating waveform that changes over time. The voltage of AC can be adjusted using transformers to suit different applications. This means that electricity can be distributed nationally at much higher voltages than household supplies, enabling large amounts of power to be moved long distances easily. The voltage of household electricity is 230 V in Europe but 110 V in North America. Additionally, some medical treatments require very low voltages which can only be achieved using AC power sources.","d009eff9-1990-4e1d-9b56-4f629c1b83f5",[1197],{"id":1198,"data":1199,"type":51,"version":25,"maxContentLevel":28},"c1ec17d9-d242-43ae-aed8-60f5a360467b",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1200,"multiChoiceCorrect":1202,"multiChoiceIncorrect":1204},[1201],"What type of electric current is used to power most electronic devices?",[1203],"Direct current (DC)",[1205,1206,1207],"Alternating current (AC)","Static current","Solar current",{"id":1209,"data":1210,"type":25,"maxContentLevel":28,"version":25,"reviews":1214},"ef9f659c-cc48-46c1-b377-5527ccfe396a",{"type":25,"title":1211,"markdownContent":1212,"audioMediaId":1213},"Voltage and potential difference","Voltage is the amount of energy required to move a unit charge from one point to another in an electric field. It can be thought of as the “push” that moves electrons through a circuit and is measured in volts (V). Voltage is related to potential difference, which is the difference in electrical potential between two points. \n\nThe voltage between two points can be calculated using Ohm's law, which states that voltage equals current multiplied by resistance. In this equation, current represents how much charge flows through a material over time while resistance measures how difficult it is for charge to flow through that material. For example, when electricity passes through copper wire with low resistance there will be less voltage drop compared to passing electricity through rubber with high resistance; thus more power will reach its destination when travelling along copper wires rather than rubber ones!\n\n ![Graph](image://ac673e6e-1b23-481e-935e-c7b6b92fa71b \"The Ohm's law equation. Image: Black-slon, CC BY-SA 4.0, via Wikimedia Commons\")\n\nIn addition, voltage has an inverse relationship with capacitance - meaning that increasing capacitance decreases voltage and vice versa. Capacitors are components used in circuits which store electrical energy and release it when needed; they are often found in electronic devices such as TVs or computers where they help regulate power supply levels.\n","e4dfb25c-628e-4ea5-95d3-6ec54fd57dd9",[1215],{"id":1216,"data":1217,"type":51,"version":25,"maxContentLevel":28},"16c45dfa-5ea7-4b7a-a0f9-5adc6bf5a983",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1218,"multiChoiceCorrect":1220,"multiChoiceIncorrect":1222},[1219],"What equation is used to calculate the voltage between two points?",[1221],"Ohm's law",[1223,1224,1225],"Coulomb's law","Faraday's law","Ampere's law",{"id":1227,"data":1228,"type":25,"maxContentLevel":28,"version":25,"reviews":1232},"77672dc6-bb2d-4a05-868d-926f22a4cf80",{"type":25,"title":1229,"markdownContent":1230,"audioMediaId":1231},"Electric circuits","Electric circuits are pathways for electrical current to flow through, and they can be either open or closed. In a closed circuit, the electric current is able to travel in a continuous loop from one point back to its starting point. Insulators are materials that do not allow electricity to pass through them easily, while conductors allow electricity to move freely. Examples of insulating materials include rubber and plastic, while copper and aluminum are examples of conducting materials.\n\nWhen an electric circuit is broken due to a faulty connection or other issue, it will cause the current flow in the circuit to stop completely. Faults in circuits can lead to damage in electronic devices as well as potential safety hazards such as fires or shocks. \n\n ![Graph](image://f6bff687-a033-47dc-8f45-6638fa130516 \"An electric circuit. Image: Meganbeckett27, CC BY-SA 3.0, via Wikimedia Commons\")\n\nSeries circuits have components connected end-to-end so that all parts receive the same amount of voltage; parallel circuits have components connected side-by-side so that each component receives its own voltage level independently from others. Both types of circuits have their advantages and disadvantages depending on what type of device they’re used for - series circuits tend to be more efficient but require more maintenance than parallel ones!\n\n","b82d6c44-eacd-40d0-ac59-d9fe5abdab07",[1233],{"id":1234,"data":1235,"type":51,"version":25,"maxContentLevel":28},"cd909be9-2015-43ae-871c-0d4ad357b51b",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1236,"binaryCorrect":1238,"binaryIncorrect":1240},[1237],"What materials do not allow electricity to pass through them easily?",[1239],"Insulators",[1241],"Conductors",{"id":1243,"data":1244,"type":25,"maxContentLevel":28,"version":25,"reviews":1247},"203ce556-697c-478e-ab26-8e1fabc4c120",{"type":25,"title":1221,"markdownContent":1245,"audioMediaId":1246},"Ohm's law states that the current in an electrical circuit is directly proportional to the voltage and inversely proportional to the resistance. This means that if you increase the voltage, then more current will flow through a given resistance; conversely, if you decrease the resistance, then more current will flow for a given voltage. Resistance can be thought of as a measure of how difficult it is for electricity to pass through something - materials like copper are good conductors because they have low resistances while materials like rubber are insulators because they have high resistances.\n\nThe unit of measurement for resistance is ohms (Ω), named after Georg Ohm who first formulated this law in 1827. The formula V = IR describes this relationship between voltage (V), current (I) and resistance (R). For example, if we know that there’s 10 volts across a resistor with 5 ohms of resistance, then we can calculate that 2 amps of current must be flowing through it using Ohm's law: 10V/5Ω = 2A.\n\nIt's important to note that not all components obey Ohm's law - transistors and diodes are two examples which do not follow this equation due to their non-linear behavior.\n\n ![Graph](image://6b6b6582-aa46-4482-b5cb-d75caa716149 \" copper wires\")","d34f45c2-49b3-406d-8f38-f3eb54df6b08",[1248],{"id":1249,"data":1250,"type":51,"version":25,"maxContentLevel":28},"df094ff2-35d5-40ce-83e4-edd32960a484",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1251,"multiChoiceCorrect":1253,"multiChoiceIncorrect":1255},[1252],"What is the unit of measurement for resistance?",[1254],"Ohms (Ω)",[1256,1257,571],"Volts (V)","Amps (A)",{"id":1259,"data":1260,"type":21,"version":25,"maxContentLevel":28,"pages":1262},"c7e6d761-e977-4f0f-add9-11c255cfbbbe",{"type":21,"title":1261},"Properties of Electrical Components",[1263,1278,1294],{"id":1264,"data":1265,"type":25,"maxContentLevel":28,"version":25,"reviews":1269},"db576f21-3a47-4817-a1ef-4a95c6f4b6ef",{"type":25,"title":1266,"markdownContent":1267,"audioMediaId":1268},"Capacitance","Capacitance is the ability of a material to store electrical charge. It is measured in Farads (F), which are equal to one coulomb per volt (C/V). Capacitors are components that use capacitance to store and release energy, and they can be found in almost all electronic circuits. They consist of two conductive plates separated by an insulating material called a dielectric, which allows them to hold onto electric charge for longer periods of time than other components.\n\nCapacitors have many uses in electronics, such as filtering out unwanted signals or providing short bursts of power when needed. For example, they can be used as part of a circuit that regulates the voltage supplied from a battery - this helps protect sensitive devices like computers from sudden surges or drops in voltage. Additionally, capacitors are often used with inductors to create simple oscillators - these generate alternating current at specific frequencies and are essential for certain types of radio transmission.\n\n ![Graph](image://d8ebb583-d42e-419c-8697-48a21ea31ab6 \"A dielectric. Image: By Papa November, CC BY-SA 3.0, via Wikimedia Commons\")","31a9c947-52ff-4bb5-8e4d-90e74149ec24",[1270],{"id":1271,"data":1272,"type":51,"version":25,"maxContentLevel":28},"835d1caa-c927-40fb-ab48-cd0e296c2515",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1273,"multiChoiceCorrect":1275,"multiChoiceIncorrect":1277},[1274],"What is the unit of measurement for capacitance?",[1276],"Farads (F)",[1188,575,1256],{"id":1279,"data":1280,"type":25,"maxContentLevel":28,"version":25,"reviews":1284},"7adb17da-b29e-48f2-b844-be1c1cb8f02d",{"type":25,"title":1281,"markdownContent":1282,"audioMediaId":1283},"Inductance","Inductance is the tendency of a material to oppose changes in electric current, measured in henrys (H). It is caused by the magnetic field generated when an electric current passes through a conductor. \n\nThis phenomenon is known as Faraday's law of induction and it states that an electromotive force will be induced in any circuit which contains a changing magnetic field. Inductors are components used to store energy in electrical circuits, usually consisting of coils or loops of wire wrapped around a core made from iron or ferrite. Inductors are often used to filter out unwanted signals or to make transformers. \n\n ![Graph](image://311d9493-0c2f-473b-92b2-931fd1ba30a0 \"An inductor. GFDL, CC BY-SA 3.0, via Wikimedia Commons\")\n\nThey can also be used as sensors - for example, inductive sensors are often used in traffic lights. Induction motors harness inductance to create mechanical energy using a rotating magnetic field. \n\nInductance is inversely proportional to frequency - that is, if the frequency of an electric current goes up, inductance goes down.\n","0adf0aab-5b51-48c3-bada-e4a71917b6bb",[1285],{"id":1286,"data":1287,"type":51,"version":25,"maxContentLevel":28},"8a067ee9-fd0f-459a-b6d9-72eeedb3964d",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1288,"multiChoiceCorrect":1290,"multiChoiceIncorrect":1292},[1289],"What is the unit of measure for inductance?",[1291],"Henrys (H)",[1293,573,575],"Faradays (F)",{"id":1295,"data":1296,"type":25,"maxContentLevel":28,"version":25,"reviews":1300},"c1f8783a-59c0-4979-a593-88d40df0e967",{"type":25,"title":1297,"markdownContent":1298,"audioMediaId":1299},"Electric Fields and magnetic fields","Electric fields are generated by electric charges, and can be visualized as lines of force radiating outward from the charge. These fields exert a force on other charged particles in their vicinity, causing them to move or accelerate. Electric fields have both magnitude and direction, and can be measured using an instrument called an electrometer. Magnetic fields are similar, but describe the influence of magnetic force. A magnetic field is created when electric current flows through a conductor such as a wire.\n\nThe Earth's magnetic field is believed to originate from its molten iron core which generates electrical currents due to convection within it.\n\nMagnetic fields and electric fields move at right angles to each other. The combined electromagnetic force acting on a charged particle is known as Lorentz Force - this is responsible for many phenomena such as magnetism in materials like iron, induction motors used in everyday appliances like washing machines, and even auroras! In addition to these effects on matter itself, electromagnetic radiation (EMR) also results from interactions between electric and magnetic fields - this includes visible light but also radio waves used for communication purposes.\n\n ![Graph](image://20511a2b-f738-4269-8f33-088b4f4cafa3 \"an electrometer\")","9dccfd0d-ef75-4e27-8fb7-2114829a0415",[1301],{"id":1302,"data":1303,"type":51,"version":25,"maxContentLevel":28},"9a4efd8b-7c6a-4270-a2ea-9e0c051418de",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1304,"multiChoiceCorrect":1306,"multiChoiceIncorrect":1308},[1305],"What is the name of the combined electromagnetic force acting on a charged particle?",[1307],"Lorentz Force",[1309,1310,1311],"Coulomb Force","Ampere Force","Faraday Force",{"id":1313,"data":1314,"type":21,"version":25,"maxContentLevel":28,"pages":1316},"870e719e-9ac9-47c8-ad8f-3cc599ec9107",{"type":21,"title":1315},"Electromagnetic Principles",[1317,1334],{"id":1318,"data":1319,"type":25,"maxContentLevel":28,"version":25,"reviews":1322},"9d781735-8590-4ab8-a33c-44209d634635",{"type":25,"title":1224,"markdownContent":1320,"audioMediaId":1321},"Michael Faraday's law of electromagnetic induction states that a changing magnetic field induces an electric current in a conductor. This phenomenon was discovered by Faraday in 1831, when he observed that moving a magnet near a coil of wire caused electricity to flow through the wire. This discovery revolutionized electrical engineering and led to the development of many modern technologies such as generators, transformers, and induction motors.\nInduction motors are used extensively today for powering appliances like mixers and air conditioners due to their efficiency and reliability.\n\n ![Graph](image://6d6190cb-95dd-4861-9fe5-a9f9cb3b6581 \"A magnetic levitation train. Image: tataquax from Japan, CC BY-SA 2.0, via Wikimedia Commons\")\n\nThey work on the principle of electromagnetic induction - when alternating current passes through coils inside the motor, it creates a magnetic field which rotates in synchronicity with the oscillating current. This in turn causes a rotor element to rotate - sometimes at very high speed - 3600 revolutions per minute is common in some motors. The speed can be controlled by varying the frequency or voltage applied to its windings.\n\nFaraday's law has also been used in medical imaging technology such as Magnetic Resonance Imaging (MRI) scanners which use powerful magnets and radio waves to create detailed images of internal organs without any invasive procedures.\n\n","a155e7be-c0ea-4fb2-b89b-7cfabe6b7827",[1323],{"id":1324,"data":1325,"type":51,"version":25,"maxContentLevel":28},"b95e4231-f4a1-47bb-b40f-a0f1b8eea7e5",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1326,"multiChoiceCorrect":1328,"multiChoiceIncorrect":1330},[1327],"What technology uses Faraday's law of electromagnetic induction to create detailed images of internal organs without any invasive procedures?",[1329],"Magnetic Resonance Imaging (MRI)",[1331,1332,1333],"X-ray Imaging","Ultrasound Imaging","Computerized Tomography (CT) Scanning",{"id":1335,"data":1336,"type":25,"maxContentLevel":28,"version":25,"reviews":1340},"8bcebb19-b7e2-45c9-bdf2-476f628f4f4a",{"type":25,"title":1337,"markdownContent":1338,"audioMediaId":1339},"Lenz's law","Lenz's law is a fundamental principle of electromagnetism that states the direction of an induced current is always such that it opposes the change in magnetic flux which produced it. This can be seen as analogous to Newton's third law of motion, which states for every action there is an equal and opposite reaction.\n\nFor example, when a magnet moves towards a coil of wire, the changing magnetic field induces an electric current in the wire according to Faraday’s law. According to Lenz’s law, this induced current will flow in such a way as to oppose the magnetic flux of the magnet - creating a repulsive force between them. \n\nThe principles behind Lenz’s law have been used extensively in modern technology from MRI scanners and induction motors, to AC generators and metal detectors.\n","6a387857-fa95-4a79-ba0f-8ffb10e65715",[1341],{"id":1342,"data":1343,"type":51,"version":25,"maxContentLevel":28},"deba4bfd-4078-4029-b3eb-4ac661566035",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1344,"multiChoiceCorrect":1346,"multiChoiceIncorrect":1347},[1345],"What law states that the direction of an induced current is always such that it opposes the change in magnetic flux which produced it?",[1337],[1348,1224,1221],"Newton's law",{"id":1350,"data":1351,"type":27,"maxContentLevel":28,"version":25,"orbs":1354},"c01df177-ec12-49af-9e3c-f74714bcfaa9",{"type":27,"title":1352,"tagline":1353},"Electromagnetic Waves","The waves that power the electromagnetic spectrum.",[1355,1410,1466],{"id":1356,"data":1357,"type":21,"version":25,"maxContentLevel":28,"pages":1359},"244616b9-5553-432f-9023-8e92743a3819",{"type":21,"title":1358},"Understanding Electromagnetic Waves",[1360,1378,1392],{"id":1361,"data":1362,"type":25,"maxContentLevel":28,"version":25,"reviews":1366},"d5c505eb-a6f5-4720-8f71-d92e58620237",{"type":25,"title":1363,"markdownContent":1364,"audioMediaId":1365},"What are electromagnetic waves","Electromagnetic waves are a form of energy that is made up of oscillating electric and magnetic fields. These fields are synchronized and at right angles to one another. Electromagnetic waves travel through space at the speed of light, which is approximately 300 million meters per second. \n\nElectromagnetic waves can be classified into different categories based on their frequency, such as radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.\n\n ![Graph](image://fee57e6f-811a-4d9a-bc7f-12d316e7ce2b \"Electromagnetic waves. Image: DECHAMMAKL, CC BY-SA 4.0, via Wikimedia Commons\")\n\nRadio waves have the longest wavelength and lowest frequency among all electromagnetic waves. Their wavelengths range from around the size of buildings to about the size of a coin. As wavelength decreases, the electromagnetic spectrum moves through microwaves, infrared radiation, visible light, ultraviolet radiation and X-rays. The shortest waves on the electromagnetic spectrum, with the highest energies, are gamma rays. Gamma rays have wavelengths less than 100 picometers (pm), around the size of atomic nuclei.\n\n","71c60fa5-449f-48e3-aaf9-25244efe6705",[1367],{"id":1368,"data":1369,"type":51,"version":25,"maxContentLevel":28},"270407c6-e18b-4333-a382-d7483d6402fc",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1370,"multiChoiceCorrect":1372,"multiChoiceIncorrect":1374},[1371],"What is the approximate speed of electromagnetic waves?",[1373],"300 million meters per second",[1375,1376,1377],"100 million meters per second","500 million meters per second","200 million meters per second",{"id":1379,"data":1380,"type":25,"maxContentLevel":28,"version":25,"reviews":1384},"c494631e-67de-4f4d-a56b-823daaf6c167",{"type":25,"title":1381,"markdownContent":1382,"audioMediaId":1383},"Properties of electromagnetic waves","Electromagnetic waves are forms of energy that travel through space extremely fast - at the rate of 299 792 458 m / s. This is exactly the speed of light. It means that electromagnetic waves can travel from Earth to the Moon in just 1.3 seconds! As far as we know, nothing travels faster. They have no mass and can travel through a vacuum, meaning they do not need any medium such as air or water to propagate.\n\n ![Graph](image://300c949c-f4d4-4088-aa03-bd216b87cb81 \"Radio waves\")\n\nThe properties of an electromagnetic wave depend on each other; higher frequencies correspond to higher energies and shorter wavelengths and vice versa. For example, radio waves have the longest wavelength and lowest frequency among all electromagnetic waves while gamma rays have the shortest wavelength and highest frequency. Electromagnetic radiation also has different effects depending on its frequency; for instance, visible light allows us to see things around us while X-rays allow doctors to look inside our bodies without surgery.\n\n","12cdab8c-b1dc-4d30-9664-8b397249f669",[1385],{"id":1386,"data":1387,"type":51,"version":25,"maxContentLevel":28},"64a39de0-2828-40e2-84b2-841490fa61fe",{"type":51,"reviewType":25,"spacingBehaviour":25,"activeRecallQuestion":1388,"activeRecallAnswers":1390},[1389],"What is the speed at which electromagnetic waves travel?",[1391],"299 792 458 m/s",{"id":1393,"data":1394,"type":25,"maxContentLevel":28,"version":25,"reviews":1398},"0993502f-96bd-4a61-a389-c1f7d8e7d79b",{"type":25,"title":1395,"markdownContent":1396,"audioMediaId":1397},"Electromagnetic spectrum","The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. It consists of seven distinct categories, each with its own unique wavelength range: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Radio waves have the longest wavelengths and lowest frequencies while gamma rays have the shortest wavelengths and highest frequencies.\n\nRadio waves are used for communication purposes such as broadcasting radio signals or transmitting data from satellites to Earth; they can travel through walls and other obstacles due to their long wavelength. Microwaves are used in microwave ovens to heat food quickly by exciting water molecules in the food with high-frequency electromagnetic radiation; they also allow us to communicate via satellite phones even when we’re far away from cellular towers. \n\nInfrared radiation has shorter wavelengths than microwaves and is emitted by warm objects like our bodies; it can be detected using thermal imaging cameras which allow us to see things due to their temperature, which would otherwise be invisible, e.g. at night. \n\nVisible light has an even shorter wavelength than infrared radiation and consists of all colors we can see with our eyes - red, orange, yellow, green, blue, indigo, violet - each color having its own unique wavelength range between 400 nanometers (violet) and 700 nanometers (red). Ultraviolet radiation has a much shorter wavelength than visible light and is responsible for sunburns when exposed too long without protection; it also helps plants photosynthesize by providing them with energy from sunlight.","ecf0facc-84fa-48fa-ab89-9fc77febf26c",[1399],{"id":1400,"data":1401,"type":51,"version":25,"maxContentLevel":28},"34d17a4a-e509-4daa-81da-9131ff3c2d5e",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1402,"multiChoiceCorrect":1404,"multiChoiceIncorrect":1406},[1403],"What type of radiation has the shortest wavelength and highest frequency?",[1405],"Gamma rays",[1407,1408,1409],"Radio waves","Infrared radiation","Visible light",{"id":1411,"data":1412,"type":21,"version":25,"maxContentLevel":28,"pages":1414},"422bcda0-3188-48ac-bb6d-19a8fe3a9638",{"type":21,"title":1413},"Types of Electromagnetic Radiation",[1415,1431,1449],{"id":1416,"data":1417,"type":25,"maxContentLevel":28,"version":25,"reviews":1420},"db826fe8-3ffe-4627-8e84-f2f0ee600376",{"type":25,"title":1407,"markdownContent":1418,"audioMediaId":1419},"Radio waves are the longest and lowest frequency type of electromagnetic radiation. Radio waves are generally considered to have frequencies between 300 gigahertz (GHz) and 3 kilohertz (KHz), with corresponding wavelengths ranging from 1 millimeter to up to 100 kilometers. For some purposes, such as radio communication, they can be divided into two categories: ground waves and sky waves. Ground waves travel parallel to the surface of the Earth, while sky waves are reflected off the ionosphere back down to Earth.\n\n\n ![Graph](image://0abc7c1d-50ca-4058-9db6-969dc2e27acd \"A satellite in space\")\n\nNatural sources of radio waves include lightning strikes which generate short bursts of energy in the form of radio signals; these signals can be detected by special receivers known as lightning detectors. Radio waves can also be artificially generated using transmitters such as those used for broadcasting radio stations or transmitting data from satellites to Earth's surface. These transmitters convert electrical signals into electromagnetic radiation which is then sent out through space at light speed using an antenna.\n\nSome radio waves can diffract around obstacles like mountains due to their long wavelengths.\n","1327e9f5-3411-44f1-9498-eecfd737a298",[1421],{"id":1422,"data":1423,"type":51,"version":25,"maxContentLevel":28},"30e996ae-1a1f-48fd-a97b-3005ea760079",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1424,"multiChoiceCorrect":1426,"multiChoiceIncorrect":1427},[1425],"What type of energy is generated by lightning strikes and can be detected by lightning detectors?",[1407],[1428,1429,1430],"Infrared waves","Gamma waves","Ultraviolet waves",{"id":1432,"data":1433,"type":25,"maxContentLevel":28,"version":25,"reviews":1437},"4c0b6db0-6719-4ea5-9c21-62a34a0f7f2f",{"type":25,"title":1434,"markdownContent":1435,"audioMediaId":1436},"Microwaves","Microwaves are a type of electromagnetic radiation with wavelengths ranging from 1 millimeter to 1 meter. Some wavelengths of microwaves have the ability to penetrate Earth's atmosphere, allowing them to be used for communication with satellites. Microwaves are also used for communication and navigation purposes on Earth.\n\n ![Graph](image://89487cb6-819f-4ac1-a49d-0861c3ac458f \"A microwave oven in use\")\n\nMicrowave ovens use microwaves as they are less strongly absorbed by food than other types of radiation, allowing them to penetrate and heat food quickly.\n\nThe cosmic microwave background (CMB) is an isotropic radiation that permeates all of space, originating from the Big Bang about 13.8 billion years ago. It has a temperature of 2.7 Kelvin (-270°C), and is most apparent at frequencies between 70 and 217 GHz - within the microwave spectrum! The CMB provides us with valuable information about our universe’s history, such as its age, composition, density and expansion rate over time. \n\nAdditionally, it serves as evidence for inflationary cosmology models which suggest that our universe underwent rapid expansion in its early stages after the Big Bang event occurred.\n","79415016-450b-4bd3-83f1-728771fb737a",[1438],{"id":1439,"data":1440,"type":51,"version":25,"maxContentLevel":28},"eea1b707-61df-4675-993b-82860dc574fd",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1441,"multiChoiceCorrect":1443,"multiChoiceIncorrect":1445},[1442],"What is the temperature of the cosmic microwave background radiation?",[1444],"2.7 Kelvin",[1446,1447,1448],"0 Kelvin","5 Kelvin","-273.15 Celsius",{"id":1450,"data":1451,"type":25,"maxContentLevel":28,"version":25,"reviews":1454},"0e1048f1-7ad0-43b2-94d2-ca043b5c846e",{"type":25,"title":1408,"markdownContent":1452,"audioMediaId":1453},"Infrared radiation is a type of electromagnetic radiation with wavelengths ranging from around 700 nanometers to 1 millimeter. It cannot be seen by the human eye, but can be sensed as heat. Infrared radiation is often divided into three categories: near infrared (NIR), mid-infrared (MIR) and far infrared (FIR). According to one classification, NIR has wavelengths between 700 nm and 1400 nm, MIR ranges from 1400 nm to 3000 nm, while FIR has wavelengths longer than 3000nm.\n\n ![Graph](image://6fe98de8-b363-4bee-bef1-424a8fe6d753 \"Someone using a remote control on a TV/\")\n\nInfrared light plays an important role in many everyday applications such as remote controls for TVs and other electronic devices which use NIR signals to transmit information. Telescopes also make use of infrared light to observe distant objects in space that are too faint or obscured by dust clouds when viewed through visible light alone. Mid-infrared spectroscopy can be used in medical diagnostics for detecting diseases like cancer at early stages, while FIR saunas may provide therapeutic benefits due to their ability to penetrate deep into the body’s tissues. Additionally, some animals including snakes such as vipers have evolved special organs called pit organs which allow them to detect infrared frequencies emitted by warm blooded prey even in complete darkness!\n\n","753acd6b-409e-470c-988b-a745d12a6a82",[1455],{"id":1456,"data":1457,"type":51,"version":25,"maxContentLevel":28},"6c86854f-3f6c-4be1-95c9-0e1382cc26cd",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1458,"multiChoiceCorrect":1460,"multiChoiceIncorrect":1462},[1459],"What range of wavelengths does infrared radiation have?",[1461],"700 nanometers to 1 millimeter",[1463,1464,1465],"400 nanometers to 1 millimeter","700 nanometers to 2 millimeters","400 nanometers to 2 millimeters",{"id":1467,"data":1468,"type":21,"version":25,"maxContentLevel":28,"pages":1470},"389c5945-658c-4a5f-9e16-8c3c824d23d5",{"type":21,"title":1469},"Applications of Electromagnetic Waves",[1471,1486,1503,1520],{"id":1472,"data":1473,"type":25,"maxContentLevel":28,"version":25,"reviews":1476},"46889d50-67d8-4bb8-8105-0b4709dc97f9",{"type":25,"title":1409,"markdownContent":1474,"audioMediaId":1475},"Visible light is a type of electromagnetic radiation with wavelengths ranging from around 380 nanometers to around 700 nanometers. This range of wavelengths corresponds to the colors we can see, from violet at the shortest wavelength and highest frequency, to red at the longest wavelength and lowest frequency. When visible light enters our eyes, it passes through the cornea which refracts it onto the lens where it is focused on the retina. The rods and cones in our retinas then convert this light into electrical signals that are sent to our brains for processing.\n\n ![Graph](image://47dca1a2-e824-4a5e-b78b-c5d048463191 \"A 3D printing machine. Image: ESA, CC BY-SA IGO 3.0, CC BY-SA 3.0 IGO, via Wikimedia Commons\")\n\nVisible light has many applications in modern technology such as visible lasers, barcode scanners, CD/DVD players and 3D printing machines.","8a6ebbab-1ad3-4c88-9d82-ce0868aa7f3d",[1477],{"id":1478,"data":1479,"type":51,"version":25,"maxContentLevel":28},"837c12c6-2865-4796-9e7c-1e66b2fc775b",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1480,"multiChoiceCorrect":1482,"multiChoiceIncorrect":1483},[1481],"What type of electromagnetic radiation has a wavelength range of 380 to 700 nanometers?",[1409],[1408,1484,1485],"Ultraviolet radiation","X-ray radiation",{"id":1487,"data":1488,"type":25,"maxContentLevel":28,"version":25,"reviews":1491},"a55a0229-425c-4e4d-858b-81a329f499b6",{"type":25,"title":1484,"markdownContent":1489,"audioMediaId":1490},"\n ![Graph](image://699567ad-260e-45d3-8cb4-c5fc1d90cf95 \"Someone standing in the sun\")\n\nUltraviolet radiation is a type of electromagnetic radiation generally considered to have wavelengths ranging from 100 nanometers to 400 nanometers. It is divided into three categories: UVA, UVB and UVC. UVA has the longest wavelength and lowest energy, while UVC has the shortest wavelength and highest energy.\n\nThe sun is one of the most common sources of ultraviolet radiation, emitting both UVA and UVB rays which can cause skin damage such as sunburns or even skin cancer if exposed for too long without protection. Other sources include black lights used in nightclubs, welding arcs, tanning beds and germicidal lamps used to sterilize objects by killing bacteria on their surfaces.\n\nUltraviolet radiation can also be used for beneficial purposes such as creating fluorescent effects in paints or fabrics that glow under certain lighting conditions. Additionally, it can be used to sterilize medical instruments by breaking down DNA molecules within microorganisms so they cannot reproduce anymore. This process is known as ultraviolet germicidal irradiation (UVGI).\n","b91d5888-f9b1-49c7-8a39-981129e0dc52",[1492],{"id":1493,"data":1494,"type":51,"version":25,"maxContentLevel":28},"53bcd083-4e72-403c-859f-913622a542c5",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1495,"multiChoiceCorrect":1497,"multiChoiceIncorrect":1499},[1496],"What process is used to break down DNA molecules within microorganisms so they cannot reproduce anymore?",[1498],"Ultraviolet germicidal irradiation (UVGI)",[1500,1501,1502],"Ultraviolet sterilization","Ultraviolet disinfection","Ultraviolet sanitization",{"id":1504,"data":1505,"type":25,"maxContentLevel":28,"version":25,"reviews":1509},"d36c2fff-be48-4651-a060-96e89f7e6ab4",{"type":25,"title":1506,"markdownContent":1507,"audioMediaId":1508},"X-rays","X-rays are a type of electromagnetic radiation with wavelengths ranging from 0.01 nanometers to 10 nanometers, making them shorter than ultraviolet and visible light but longer than gamma rays. X-rays can be divided into two categories: soft x-rays (wavelengths between 0.1 and 10 nm) and hard x-rays (wavelengths between 0.2 and 0.01 nm).\n\n ![Graph](image://cb81e9d7-0235-4981-bb30-71d2cdcea0bb \"An X-ray machine. Image: Nick Smith photography, CC BY-SA 3.0, via Wikimedia Commons\")\n\nSoft x-rays have lower energy levels than hard x-rays. Because of their penetrating ability, hard x-rays can be used to see inside objects which are otherwise opaque. X-ray machines used in hospitals use both types of radiation depending on the application required; for example, mammograms require low energy soft x-ray beams while high energy hard x-ray beams can be used to look for fractures in bones.\n\nMost forms of X–ray cannot penetrate Earth's atmosphere due to its protective ozone layer which absorbs most incoming radiation before it reaches the surface; however some cosmic ray particles do make it through this barrier and can cause damage if exposed for too long without protection.\n\n","a9de55d1-e7c7-4346-ae52-d7cd226768e0",[1510],{"id":1511,"data":1512,"type":51,"version":25,"maxContentLevel":28},"b832334b-242c-42c8-8fdd-3995e758ba4d",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1513,"multiChoiceCorrect":1515,"multiChoiceIncorrect":1517},[1514],"What type of radiation has a wavelength between 0.01 and 0.2 nanometers?",[1516],"Hard X-rays",[1518,1519,1405],"Soft X-rays","Ultraviolet light",{"id":1521,"data":1522,"type":25,"maxContentLevel":28,"version":25,"reviews":1525},"f32c0b63-d82b-4e92-98d7-a78b35391f63",{"type":25,"title":1405,"markdownContent":1523,"audioMediaId":1524},"Gamma rays are a form of electromagnetic radiation, with wavelengths under 10 picometers (pm). This is incredibly short - a picometer is a trillionth of a meter. They have the highest frequency and energy of all forms of light, and can penetrate through most materials more easily than X-rays. Gamma rays are produced by the most extremely energetic objects in the universe - including neutron stars and supernova explosions. They are also produced during nuclear reactions such as those in radioactive decay or in nuclear explosions.\n\nUnfortunately, gamma rays are also highly dangerous for living organisms due to their ability to ionize atoms and molecules they come into contact with. This can damage DNA and tissues within bodies. Fortunately, most gamma rays do not penetrate Earth's atmosphere - it acts as a shield against them, protecting us from their potentially harmful effects on our bodies. Exposure to large doses of gamma radiation can cause radiation sickness and severe damage including cell death, genetic mutations and cancerous growths. Even small amounts can lead to increased risk of developing certain types of cancers later in life.\n","76865514-c46e-4a54-8739-b543860eca1d",[1526],{"id":1527,"data":1528,"type":51,"version":25,"maxContentLevel":28},"89ac80ac-2dff-49f3-9eb5-ee5305de550c",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1529,"multiChoiceCorrect":1531,"multiChoiceIncorrect":1532},[1530],"What is the highest frequency and energy form of electromagnetic radiation?",[1405],[1407,1434,1430],{"id":1534,"data":1535,"type":27,"maxContentLevel":28,"version":25,"orbs":1538},"9a79ef77-330d-46e5-855e-4895ea1516be",{"type":27,"title":1536,"tagline":1537},"Thermodynamics","The study of the relationship between heat and other forms of energy.",[1539,1592,1648],{"id":1540,"data":1541,"type":21,"version":25,"maxContentLevel":28,"pages":1543},"db5ef417-8e4d-4a9d-b4ca-b65fa71dd517",{"type":21,"title":1542},"Fundamentals of Thermodynamics",[1544,1560,1576],{"id":1545,"data":1546,"type":25,"maxContentLevel":28,"version":25,"reviews":1550},"115f7b6d-0d69-4aec-beab-005baa358b37",{"type":25,"title":1547,"markdownContent":1548,"audioMediaId":1549},"The laws of thermodynamics","Thermodynamics is the study of the relationship between heat and other forms of energy. It is a fundamental field of physics, underpinned by four laws which describe how energy behaves in different systems. The first law states that energy can neither be created nor destroyed; it can only change form. This means that when heat moves from one object to another, the total amount of energy remains constant.\n\n ![Graph](image://f57a70ec-eca4-4a01-8fae-bb56268ff720 \"Robert Boyle\")\n\nThe second law explains why some processes are irreversible: entropy always increases over time as heat flows from hotter objects to cooler ones until equilibrium is reached. Entropy measures the degree of disorder in a system, so this law implies that all natural processes tend towards greater disorder or chaos over time.\n\nThe third law states that as temperatures approach absolute zero, entropy tends to a constant value. Essentially, the third law states that if an object reached absolute zero, its atoms would stop moving.\n\nIn addition to these three laws, what is commonly known as the zeroth law of thermodynamics states that if two bodies are in equilibrium with a third body, they are also in equilibrium with each other.\n\n","3616dda5-a6e5-422e-99a6-156bfdd2a84e",[1551],{"id":1552,"data":1553,"type":51,"version":25,"maxContentLevel":28},"e9898711-b7ac-4e99-881b-7a7bdaa837ae",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1554,"binaryCorrect":1556,"binaryIncorrect":1558},[1555],"How many laws underpin the study of thermodynamics?",[1557],"Four",[1559],"Two",{"id":1561,"data":1562,"type":25,"maxContentLevel":28,"version":25,"reviews":1566},"aeb793ac-3410-4676-9fca-d2532c1ba3bf",{"type":25,"title":1563,"markdownContent":1564,"audioMediaId":1565},"The first law of thermodynamics","The first law of thermodynamics states that energy can neither be created nor destroyed, but only changed from one form to another. This is known as the conservation of energy and it means that in an isolated system - without any matter or energy coming in or going out - the total energy must remain constant. \n\nIn other words, when work is done on a system, the total amount of energy remains constant; any increase in one type of energy must be balanced by a decrease in another type.\n\n ![Graph](image://cad9586a-786a-4f9c-aafd-fd2f6790546d \"French physicist Sadi Carnot\")\n\nFor example, when a car brakes its kinetic energy is converted into heat due to friction between the brake pads and wheels. Similarly, we can understand metabolic processes in the human body by using the first law of thermodynamics. We obtain energy from the environment by consuming food, and this energy is used to do work, transferred as heat or stored as chemical energy in the body.\n\n","6ef73762-00de-4a4d-b0ce-fbb252525f00",[1567],{"id":1568,"data":1569,"type":51,"version":25,"maxContentLevel":28},"a419ccf2-cc13-4f12-a95b-97f19372b976",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1570,"binaryCorrect":1572,"binaryIncorrect":1574},[1571],"What does the first law of thermodynamics state about energy?",[1573],"Energy can neither be created nor destroyed",[1575],"Energy can be created or destroyed",{"id":1577,"data":1578,"type":25,"maxContentLevel":28,"version":25,"reviews":1582},"0a4dfd4b-86d6-41ce-b0f2-d0a8efb4d3cf",{"type":25,"title":1579,"markdownContent":1580,"audioMediaId":1581},"The second law of thermodynamics","\n ![Graph](image://373e66fd-6c5d-4d46-bf57-6f6557a505cf \"A cup of hot coffee on a table\")\n\nThe second law of thermodynamics states that the entropy, or the degree of disorder in a system, of the universe always increases over time. This means that all natural processes tend towards greater chaos and disorganization as energy is dispersed from hotter to cooler objects. For example, when you leave a cup of coffee on the table it will eventually cool down due to heat transfer from the hot liquid to its surroundings.\n\nAdditionally, the second law of thermodynamics states that if a process is irreversible, it must result in an increase in the combined entropy of the system and the environment. A burning campfire is an example of increasing entropy in an irreversible process. As the wood burns, energy and vapors are released, spreading in an expanding cloud and leaving behind nothing but ashes. The remnants of a fire will never be turned back into wood. The foundations for the second law of thermodynamics were laid by the scientist Rudolf Clausius in 1850.\n","d4d53fef-cb69-4749-a93d-703627871025",[1583],{"id":1584,"data":1585,"type":51,"version":25,"maxContentLevel":28},"e9d918b6-c085-4414-8db5-f5778d008e6b",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1586,"multiChoiceCorrect":1588,"multiChoiceIncorrect":1590},[1587],"Who laid the foundations for the second law of thermodynamics in 1850?",[1589],"Rudolf Clausius",[74,72,1591],"Marie Curie",{"id":1593,"data":1594,"type":21,"version":25,"maxContentLevel":28,"pages":1596},"6d098f43-4a2a-4500-a131-519f2f8baf96",{"type":21,"title":1595},"Applications of Thermodynamics",[1597,1613,1630],{"id":1598,"data":1599,"type":25,"maxContentLevel":28,"version":25,"reviews":1603},"1b674f32-546f-4e84-b65a-f03a8b47de5e",{"type":25,"title":1600,"markdownContent":1601,"audioMediaId":1602},"Heat engines and efficiency","Heat engines are devices that convert thermal energy into mechanical work. They operate by transferring heat from a hot place to a cold one, and diverting some of this energy into mechanical energy. The most common heat engines are internal combustion engines. The efficiency of engines such as these is determined by how much useful work they can produce compared to the amount of energy put into them.\n\n ![Graph](image://1b39b64f-30c9-4ca9-b128-8057b7530fda \"A Heat engine\")\n\nThe Second Law of Thermodynamics states that it is impossible for any heat engine to reach 100% efficiency due to entropy; some energy will always be lost as waste heat during the process. This means that no matter how advanced an engine may be, there will always be some inefficiency associated with it. Heat engines commonly reach only around 30-50% efficiency, as a result of practical constraints.\n\nDespite this limitation, engineers continue to strive towards greater efficiencies through improved designs and materials - such as turbochargers, which increase air pressure within cylinders for more powerful combustion.\n","8613150e-a479-46a2-b36b-3d7e0009da3b",[1604],{"id":1605,"data":1606,"type":51,"version":25,"maxContentLevel":28},"0d7f08ae-8283-4e09-a7ce-3a7704802924",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1607,"binaryCorrect":1609,"binaryIncorrect":1611},[1608],"What is the maximum efficiency that a heat engine can reach, due to entropy?",[1610],"30-50%",[1612],"100%",{"id":1614,"data":1615,"type":25,"maxContentLevel":28,"version":25,"reviews":1619},"1a096114-c94b-4bb0-9afd-7508bad221cb",{"type":25,"title":1616,"markdownContent":1617,"audioMediaId":1618},"The Carnot cycle"," ![Graph](image://6df5f1f7-9f9c-435b-bcb6-6e21b498e572 \"The Carnot cycle\")\n\nThe Carnot cycle is a theoretical thermodynamic cycle that describes the most efficient way to convert heat into work. It consists of four phases: isothermal expansion, adiabatic expansion, isothermal compression and adiabatic compression. During the first two phases, heat is transferred to an ideal gas in the system from a hot reservoir and causes the gas to expand and do work on its surroundings. During the second two phases, heat leaves the system as the gas contracts. This process can be repeated indefinitely for maximum efficiency.\n\nUnfortunately, this idealized model cannot be achieved in reality due to friction and other losses associated with real-world engines. Nevertheless, its principles are still used today in modern engineering designs such as refrigerators which use a reversed analogous cycle to cool their interiors by transferring heat outwards instead of inwards.\n\n","af7cdc0d-87b7-4963-bd92-903f63a7b63c",[1620],{"id":1621,"data":1622,"type":51,"version":25,"maxContentLevel":28},"a00deb5e-0cc8-438e-a6f5-44f2b37fd42a",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1623,"multiChoiceCorrect":1625,"multiChoiceIncorrect":1626},[1624],"What is the theoretical thermodynamic cycle that describes the most efficient way to convert heat into work?",[1616],[1627,1628,1629],"The Rankine cycle","The Joule cycle","The Brayton cycle",{"id":1631,"data":1632,"type":25,"maxContentLevel":28,"version":25,"reviews":1636},"f11b3097-a462-410b-a4bd-122c9aff0ea2",{"type":25,"title":1633,"markdownContent":1634,"audioMediaId":1635},"Entropy","Entropy is a measure of the amount of energy in a system that is unavailable for doing work. It can be thought of as the disorder or randomness within a system, and it tends to increase over time. This means that any process which involves an increase in entropy will also involve an increase in disorder. For example, when ice melts into liquid water, its molecules become more disordered and spread out; this results in an increase in entropy and thus less energy available to do work.\n\n ![Graph](image://cced5d16-2332-4e27-b7a1-4ed75eb0a8fe \"Ice melting\")\n\nThe Second Law of Thermodynamics states that the entropy of the universe always increases over time, meaning that all processes tend towards greater disorder and lower efficiency. This law has far-reaching implications for our universe: without it, stars would not burn fuel efficiently enough to sustain life on Earth! In fact, some scientists believe that the increasing entropy of our universe may eventually lead to its eventual heat death - at which point no free thermodynamic energy remains in the universe.\n\n","52ecc814-ece2-4a32-9f54-1b7744423e1a",[1637],{"id":1638,"data":1639,"type":51,"version":25,"maxContentLevel":28},"c326fc12-736b-47b9-a7bd-ecc8ecce7a85",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1640,"multiChoiceCorrect":1642,"multiChoiceIncorrect":1644},[1641],"What law states that the entropy of the universe always increases over time?",[1643],"The Second Law of Thermodynamics",[1645,1646,1647],"The First Law of Thermodynamics","The Third Law of Thermodynamics","The Fourth Law of Thermodynamics",{"id":1649,"data":1650,"type":21,"version":25,"maxContentLevel":28,"pages":1652},"75a7e9cb-f339-415e-8414-9426fb6356f5",{"type":21,"title":1651},"Advanced Thermodynamic Concepts",[1653,1669,1687,1705],{"id":1654,"data":1655,"type":25,"maxContentLevel":28,"version":25,"reviews":1659},"5f94b384-9655-4b7f-94d6-1c07d0a9ff55",{"type":25,"title":1656,"markdownContent":1657,"audioMediaId":1658},"Gibbs free energy","Gibbs free energy is a thermodynamic quantity that describes the maximum amount of work which can be done by a closed system. It can also determine whether a reaction will occur spontaneously or not. It is calculated using enthalpy and entropy, two other thermodynamic quantities. Enthalpy measures the total energy of a system, including both heat and work; it can be worked out by adding the internal energy of a system to the product of its temperature and pressure. \n\nEntropy measures the amount of energy in a system that is unavailable for doing work. Gibbs free energy is calculated by deducting the product of entropy and temperature from enthalpy. This gives us an indication of how much useful work can be extracted from any given process - if this value is negative then the reaction will occur spontaneously; if positive then it won't.","336827a2-d655-4110-8ab1-de5f6a317e13",[1660],{"id":1661,"data":1662,"type":51,"version":25,"maxContentLevel":28},"7064b8fd-0c99-45e5-8918-a3c3b597da16",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1663,"binaryCorrect":1665,"binaryIncorrect":1667},[1664],"How is Gibbs free energy calculated?",[1666],"By deducting the product of entropy and temperature from enthalpy",[1668],"By adding the internal energy of a system to the product of its temperature and pressure",{"id":1670,"data":1671,"type":25,"maxContentLevel":28,"version":25,"reviews":1675},"d1a365fa-5b14-40e7-a337-02ee6ac60a30",{"type":25,"title":1672,"markdownContent":1673,"audioMediaId":1674},"Phase changes and phase diagrams"," ![Graph](image://f8b1f5f9-e59c-4413-b8be-dee5ad1d6c6d \"The phase from solid to liquid\")\n\nThe most common states of matter are solid, liquid and gas. Solids have a fixed shape and volume, liquids take the shape of their container but maintain a constant volume, while gases fill their containers completely and expand or contract to match changes in pressure. Common phase changes between these states include melting (solid to liquid), vaporization (liquid to gas) and sublimation (solid to gas).\n\nPhase diagrams are graphical representations of how temperature and pressure affect the state of a substance. They show which phases will be present at different temperatures and pressures, as well as the boundaries between them. For example, water's phase diagram shows that it can exist as ice below 0°C at atmospheric pressure; above this point it melts into liquid water until 100°C when it boils off into steam. By plotting points on such diagrams we can gain insight into how substances behave under different conditions - for instance why some materials become brittle when cooled too quickly.\n\n","6332c5ff-62a0-4379-8843-6657a2a45bc4",[1676],{"id":1677,"data":1678,"type":51,"version":25,"maxContentLevel":28},"cf030b60-0466-45fa-8bcc-866f9892f990",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1679,"multiChoiceCorrect":1681,"multiChoiceIncorrect":1683},[1680],"What type of diagram is used to show how temperature and pressure affect the state of a substance?",[1682],"Phase diagram",[1684,1685,1686],"Pressure diagram","Temperature diagram","Graphical diagram",{"id":1688,"data":1689,"type":25,"maxContentLevel":28,"version":25,"reviews":1693},"c7fd67af-0a0e-4406-80cd-514af56e4104",{"type":25,"title":1690,"markdownContent":1691,"audioMediaId":1692},"Ideal gases","An ideal gas is a theoretical concept used to describe the behavior of gases under certain conditions. It assumes that all molecules in the gas have no interactions with each other, allowing them to move freely, randomly, and independently. This simplifies calculations when considering thermodynamic processes such as expansion or compression, making it easier to predict how a real-world system will behave.\n\n ![Graph](image://c800dc8c-aa84-4925-9690-559d24fcb957 \"The ideal gas equation\")\n\nAt standard temperature and pressure (STP), many common gases can be considered ideal for the purposes of scientists, including nitrogen, oxygen, hydrogen and carbon dioxide. These gases obey the Ideal Gas Law which states that PV = nRT where P is pressure, V is volume, n is number of moles of gas present, R is the ideal gas constant, and T is temperature in Kelvin. The Ideal Gas Law also explains why some substances become lighter when they are heated: because their molecules spread out further due to increased thermal energy causing them to take up more space per unit mass.\n\n","045ca9ae-2ca8-4cab-961c-7abe999002af",[1694],{"id":1695,"data":1696,"type":51,"version":25,"maxContentLevel":28},"faa16e4d-243f-4389-a101-8b1926f8c56f",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1697,"multiChoiceCorrect":1699,"multiChoiceIncorrect":1701},[1698],"What law explains why some substances become lighter when they are heated?",[1700],"The Ideal Gas Law",[1702,1703,1704],"The Kinetic Theory of Gases","The Gas Laws","The Law of Conservation of Mass",{"id":1706,"data":1707,"type":25,"maxContentLevel":28,"version":25,"reviews":1711},"5cbdb60f-5f07-4e7d-9757-61d0f6b329b4",{"type":25,"title":1708,"markdownContent":1709,"audioMediaId":1710},"Real gases and the van der Waals equation","Real gases differ from ideal gases in that they have molecules which take up a finite volume and have attractive forces between them. At high pressures, the volume of most real gases is higher than the ideal gas law predicts. At sufficiently low temperatures, attractive forces cause the molecules to stick together more easily, leading to gases condensing into liquids.\n\n\nThe van der Waals equation takes these effects into account and provides a better description of real gas behavior than the Ideal Gas Law. It includes two additional terms: one for molecular size and another for intermolecular attraction. \n\nThese terms become increasingly important as pressure or temperature increases - for example when carbon dioxide is compressed at room temperature it behaves very differently than predicted by the Ideal Gas Law!\n\nInterestingly enough, this equation was first proposed by Dutch physicist Johannes Diderik van der Waals back in 1873 - over 150 years ago! Since then it has been used extensively to model real-world systems such as combustion engines and refrigeration cycles. Today it remains an invaluable tool for understanding thermodynamics on both macroscopic and microscopic scales.\n\n","1dd9e45b-2cd3-4ba4-a34f-1a9797a19258",[1712,1721],{"id":1713,"data":1714,"type":51,"version":25,"maxContentLevel":28},"32e41389-2333-4b72-bcbd-90f57914b96e",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1715,"binaryCorrect":1717,"binaryIncorrect":1719},[1716],"When was the van der Waals equation first proposed?",[1718],"1873",[1720],"1883",{"id":1722,"data":1723,"type":51,"version":25,"maxContentLevel":28},"9161c726-0886-47f1-bf59-5ff6cd25ef3d",{"type":51,"reviewType":25,"spacingBehaviour":25,"activeRecallQuestion":1724,"activeRecallAnswers":1726},[1725],"What equation is used to provide a better description of real gas behavior than the Ideal Gas Law?",[1727],"Van der Waals equation",{"id":1729,"data":1730,"type":27,"maxContentLevel":28,"version":25,"orbs":1733},"0c7255f6-7154-474e-bf60-5c653e366c81",{"type":27,"title":1731,"tagline":1732},"Nuclear Physics","The physics governing activity within atomic nuclei.",[1734,1793,1850],{"id":1735,"data":1736,"type":21,"version":25,"maxContentLevel":28,"pages":1738},"5640dd39-0c77-4176-b39e-09057d9500da",{"type":21,"title":1737},"The Structure and Forces of the Atom",[1739,1757,1775],{"id":1740,"data":1741,"type":25,"maxContentLevel":28,"version":25,"reviews":1745},"b62ebbe3-977e-4716-b31b-a39aba6270e5",{"type":25,"title":1742,"markdownContent":1743,"audioMediaId":1744},"The structure of the atom","At the heart of nuclear physics is the structure of atoms. Atoms are composed of three subatomic particles: protons, neutrons and electrons. Protons have a positive charge, while neutrons have no charge at all. Electrons carry a negative charge and orbit around the nucleus, made up of protons and neutrons, in shells or energy levels. \n\nThe number of protons in an atom determines its atomic number, which identifies it as a particular element on the periodic table. Different numbers of neutrons in nuclei results in different forms of the same element. The protons and electrons in an atom give it its charge. The sum of the masses of the protons and neutrons in a nucleus (neutrons weigh slightly more than protons) determines the atomic mass. \n\nThe arrangement within an atom is determined by quantum mechanics; each electron occupies one orbital shell with specific energy levels depending on their distance from the nucleus. This arrangement allows for chemical reactions between atoms since they can share electrons between them when forming bonds with other elements - this process is known as covalent bonding.","8da02b99-d90e-417a-b40d-961809ae3d16",[1746],{"id":1747,"data":1748,"type":51,"version":25,"maxContentLevel":28},"6baa9702-0d19-4ed3-9ed4-7e3bf175e6f8",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1749,"multiChoiceCorrect":1751,"multiChoiceIncorrect":1753},[1750],"What is the process of sharing electrons among atoms when forming bonds with other elements called?",[1752],"Covalent bonding",[1754,1755,1756],"Ionic bonding","Metallic bonding","Hydrogen bonding",{"id":1758,"data":1759,"type":25,"maxContentLevel":28,"version":25,"reviews":1763},"4aeb2f4b-fdcc-4d77-93af-475b807be6f7",{"type":25,"title":1760,"markdownContent":1761,"audioMediaId":1762},"The nuclear force","The nuclear force is the strong attractive force that binds protons and neutrons - known as nucleons - together in an atomic nucleus. It has an almost identical effect on both neutrons and protons. It was first proposed by Hideki Yukawa in 1935, who called it the meson theory of nuclear forces. This force acts over a very short distance, typically less than one femtometer (10^-15 m). It is repulsive at distances of less than 0.7 femtometers, but is most strongly attractive at 0.8 femtometers. Beyond this, it rapidly dwindles to negligible effects around 2.5 femtometers.\n\nAs the strength of the nuclear force diminishes, the repulsive electromagnetic force between protons begins to dominate and causes nuclei to become unstable. However, at shorter distances, the attractive nuclear force becomes stronger and holds nuclei together despite their positive charges. This balance between attraction and repulsion is what gives atoms their structure. The nuclear force has a vital role in storing the energy which is used in creating nuclear power or detonating nuclear weapons.\n\n ![Graph](image://a1ddc4e7-efea-4228-a62a-ad98d8179d7b \"Hideki Yukawa\")","04e8f4a5-a662-4cb1-aed2-f76936b57265",[1764],{"id":1765,"data":1766,"type":51,"version":25,"maxContentLevel":28},"1871fb2b-59d9-4b33-b94f-6629786d5071",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1767,"multiChoiceCorrect":1769,"multiChoiceIncorrect":1771},[1768],"At what distance does the nuclear force become most strongly attractive?",[1770],"0.8 femtometers",[1772,1773,1774],"0.7 femtometers","1.0 femtometers","2.5 femtometers",{"id":1776,"data":1777,"type":25,"maxContentLevel":28,"version":25,"reviews":1781},"bc3a23b8-62ce-42ec-bce1-d1d480dc5104",{"type":25,"title":1778,"markdownContent":1779,"audioMediaId":1780},"The binding energy of nuclei","Nuclear binding energy is the energy required to form a nucleus from its constituent protons and neutrons, or break it apart. It is related to the mass defect between the expected and observed nuclear mass; when nuclei are formed, some of their mass is converted into energy according to Einstein’s famous equation E=mc2. Heavier elements tend to have more binding energy than lighter ones - for example, uranium has about 7 million electron volts (MeV) of binding energy per atom compared to just 4 MeV for one form of helium!\n\nThe amount of binding energy released during a nuclear reaction can be enormous. In fact, one gram of plutonium or uranium can release around 1 MW of power a day through nuclear fission- about the same as burning 3 tons of coal in a day. This explains why fission reactions are so powerful and why fusion reactions could potentially provide an almost limitless source of clean renewable energy. In addition, understanding how much binding energy different elements possess helps us understand why certain isotopes are stable while others decay quickly over time.","a7a761fa-0910-480d-8b71-019574fcd1e6",[1782],{"id":1783,"data":1784,"type":51,"version":25,"maxContentLevel":28},"fa95b62d-e481-4bb1-b50a-2d244fc5a0aa",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1785,"multiChoiceCorrect":1787,"multiChoiceIncorrect":1789},[1786],"How much power is released from 1 gram of plutonium or uranium per day?",[1788],"1 MW",[1790,1791,1792],"1 kW","1 GW","1 MW/h",{"id":1794,"data":1795,"type":21,"version":25,"maxContentLevel":28,"pages":1797},"adff0064-9c4d-49e7-9a4d-5119523bccde",{"type":21,"title":1796},"Radioactivity and Decay",[1798,1814,1832],{"id":1799,"data":1800,"type":25,"maxContentLevel":28,"version":25,"reviews":1804},"b7728a44-c3e4-42ac-8b89-30248efccac7",{"type":25,"title":1801,"markdownContent":1802,"audioMediaId":1803},"Radioactivity","Radioactivity is the process by which unstable nuclei emit radiation or particles in order to become more stable. This occurs when a nucleus has an imbalance of protons and neutrons, resulting in an excess of energy that must be released for it to reach equilibrium. \n\nFor example, uranium-235 is unstable due to excessive repulsive forces between protons in its nucleus. It emits alpha particles - consisting of 2 neutrons and 2 protons - with the resulting product of thorium-231. These atoms in themselves are unstable, and continue to undergo radioactive decay, with the eventual product of the stable lead-207.\n\nThe rate at which radioactive decay occurs can vary greatly depending on the element involved; some elements such as uranium-238 have half lives measured in thousands or millions of years while others like technetium-99m have half lives measured in days or even hours! The half life of an element is the time it takes for half the sample to decay through radioactivity.\n\n ![Graph](image://a935fa88-7e4e-41f3-804b-be1341ed9f3b \"An illustration of nuclear fusion. Image: Haasrm, CC BY-SA 3.0 , via Wikimedia Commons\")","a135be05-bf95-421e-baf7-709448d02444",[1805],{"id":1806,"data":1807,"type":51,"version":25,"maxContentLevel":28},"73e37dcb-50c3-407b-9572-7647a4eb61b7",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1808,"binaryCorrect":1810,"binaryIncorrect":1812},[1809],"What is the result of uranium-235 emitting alpha particles?",[1811],"Thorium-231",[1813],"Lead-207",{"id":1815,"data":1816,"type":25,"maxContentLevel":28,"version":25,"reviews":1820},"a837dd55-e7c2-4bfc-89f4-a7014c8a0243",{"type":25,"title":1817,"markdownContent":1818,"audioMediaId":1819},"Explain the terms Alpha, beta, and gamma decay","Alpha, beta and gamma decay are all forms of radioactive decay. Alpha particles consist of two protons and two neutrons, while beta particles are electrons or positrons emitted from the nucleus. Gamma decay involves a loss of energy by the nucleus. Gamma radiation is highly energetic and can penetrate matter more deeply than alpha or beta radiation.\n\nAlpha and beta decays differ from gamma decay in that they involve a change in the number of protons or neutrons within an atom's nucleus; this is known as transmutation. In alpha decay, a heavy element such as uranium will emit an alpha particle to become a lighter element like thorium. Similarly, in beta decay, a neutron is turned into a proton when an electron is emitted by the nucleus, or a proton is turned into a neutron when a positron is emitted. This changes the nature of the atom by altering its atomic number (the number of protons) and mass number (the total number of nucleons - protons plus neutrons).\n\nIn contrast, gamma radiation does not cause any transmutation since it only involves energy being released without changing the composition of the atom itself.\n\n ![Graph](image://e65e4e6b-0364-47cd-ab32-475a86efe341 \"a depiction of alpha or beta decay\")","d8eb9e72-43ba-45fb-8c0a-23a5e92be1ed",[1821],{"id":1822,"data":1823,"type":51,"version":25,"maxContentLevel":28},"b6be8a70-bd6a-475e-a980-bf044d2a1037",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1824,"multiChoiceCorrect":1826,"multiChoiceIncorrect":1828},[1825],"What type of decay does not cause any transmutation?",[1827],"Gamma decay",[1829,1830,1831],"Alpha decay","Beta decay","Delta decay",{"id":1833,"data":1834,"type":25,"maxContentLevel":28,"version":25,"reviews":1838},"4286f82a-8cc3-4092-920f-8248dc7caed4",{"type":25,"title":1835,"markdownContent":1836,"audioMediaId":1837},"Nuclear reactions","Nuclear reactions are processes that involve changes in the nucleus of an atom. These include nuclear fusion or nuclear fission, both of which release large amounts of energy.\n\nIn nuclear fusion, two light nuclei combine to form a heavier one, releasing energy in the process. This is what powers stars like our sun and is responsible for creating elements heavier than iron. Nuclear fission involves splitting a heavy nucleus into two lighter ones, also releasing energy in the process. This type of reaction has been harnessed to generate electricity on Earth through power plants such as those found at Chernobyl and Fukushima Daiichi.\n\nThe amount of energy released by these reactions is immense; it takes just 1 gram (0.035 ounces) of uranium-235 to produce as much energy as burning 3 tons (3000 kilograms) of coal! The potential applications for this technology are vast but must be used responsibly due to its destructive capabilities if not handled correctly. Historically, it hasn’t been possible for humans to produce energy using nuclear fusion, but scientific advances have changed that. In December 2022, scientists were able to produce an energy gain using nuclear fusion - opening up exciting possibilities for the future.\n","3d77fa0e-0c72-4187-93c3-d3cd7a64ce37",[1839],{"id":1840,"data":1841,"type":51,"version":25,"maxContentLevel":28},"b6175b2d-248c-4e94-abb4-49e9f1b96859",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1842,"multiChoiceCorrect":1844,"multiChoiceIncorrect":1846},[1843],"What type of reaction is used to generate electricity on Earth through power plants such as those found at Chernobyl and Fukushima Daiichi?",[1845],"Nuclear fission",[1847,1848,1849],"Nuclear fusion","Nuclear decay","Nuclear transmutation",{"id":1851,"data":1852,"type":21,"version":25,"maxContentLevel":28,"pages":1854},"3217b6a2-50d7-47ab-baf0-441d85f7ccf9",{"type":21,"title":1853},"Nuclear Reactions and Applications",[1855,1871],{"id":1856,"data":1857,"type":25,"maxContentLevel":28,"version":25,"reviews":1861},"2ee1428b-9c5b-4282-ad5d-e0ac175cbc69",{"type":25,"title":1858,"markdownContent":1859,"audioMediaId":1860},"Artificial transmutation","Artificial transmutation is the process of transforming one element into another through nuclear reactions. It involves manipulating the nucleus of an atom to change its number of protons and neutrons. This can be done by bombarding it with particles such as alpha particles or protons.\n\nThe particles used in artificial transmutation include protons and neutrons. Protons have a positive charge while neutrons have no charge; both are found in the nucleus of atoms. By changing the number of these subatomic particles within an atom’s nucleus, different elements can be created from existing ones.\n\nOne example of artificial transmutation is nitrogen-14 being transformed into oxygen-17 through bombardment with alpha particles (helium nuclei). In this reaction two protons and two neutrons are added to nitrogen-14's seven protons and seven neutrons to create oxygen-17 which has eight protons and nine neutrons plus an atom of hydrogen. Thus the atom’s atomic number is changed from 7 to 8! \n\nArtificial transmutation has also been used for medical purposes such as creating radioactive isotopes for use in cancer treatments or imaging scans like PET scans (positron emission tomography).\n\n ![Graph](image://3bb2a7e1-8da1-4cc5-a06c-9b75f3c77f72 \"someone undergoing a PET scan\")","cfe73137-a4d6-4bfa-b8fc-d3bcc36cc29b",[1862],{"id":1863,"data":1864,"type":51,"version":25,"maxContentLevel":28},"f381e50b-5c82-409d-a15a-b80688aefc23",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1865,"multiChoiceCorrect":1867,"multiChoiceIncorrect":1868},[1866],"What is the process of transforming one element into another through nuclear reactions called?",[1858],[1731,1869,1870],"Nuclear Fission","Nuclear Fusion",{"id":1872,"data":1873,"type":25,"maxContentLevel":28,"version":25,"reviews":1877},"556e39a9-75c8-4291-9065-8e653cfe3209",{"type":25,"title":1874,"markdownContent":1875,"audioMediaId":1876},"Nuclear reactors","Nuclear reactors are used to generate electricity by harnessing the energy released from nuclear fission reactions. In a typical reactor, uranium fuel rods are placed in a core and bombarded with neutrons which cause the uranium atoms to split into smaller atoms, releasing heat energy. This heat is then used to boil water which produces steam that drives turbines connected to generators, producing electricity.\n\nThe main benefit of nuclear power is its efficiency; one kilogram of uranium can produce as much energy as burning 2.7 million kilograms of coal! Nuclear reactors also have low emissions compared to other sources of energy such as fossil fuels and do not contribute significantly to global warming or air pollution. Additionally, they require less land than other forms of power generation such as wind turbines.\n\n ![Graph](image://ff6034b3-a99c-45ae-8057-268815af78d5 \"a nuclear reactor. Image: Rama, CC BY-SA 2.0 FR, via Wikimedia Commons\")\n\nHowever, there are some drawbacks associated with nuclear power plants including safety concerns due to potential radiation leaks and long-term storage issues for radioactive waste products produced during operation. Furthermore, building new reactors requires large investments in infrastructure and technology which can be expensive and time consuming. Despite these drawbacks though, many countries around the world continue to use nuclear power for their electricity needs.\n","991b23ac-63ec-4613-ae35-f5f9871d926b",[1878],{"id":1879,"data":1880,"type":51,"version":25,"maxContentLevel":28},"ac37c8ef-27ab-44d7-bb66-45139002b774",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1881,"multiChoiceCorrect":1883,"multiChoiceIncorrect":1885},[1882],"What is one advantage of nuclear reactors compared to other sources of energy?",[1884],"Low emissions",[1886,1887,1888],"Low infrastructure requirements","Low waste","Low cost of power plants",{"id":1890,"data":1891,"type":27,"maxContentLevel":28,"version":25,"orbs":1894},"3f69326c-4e59-497f-9244-fcb59da7c59b",{"type":27,"title":1892,"tagline":1893},"Quantum Mechanics","Where Newtonian physics stops working.",[1895,1965],{"id":1896,"data":1897,"type":21,"version":25,"maxContentLevel":28,"pages":1899},"3414d060-cbc5-4f30-a2eb-472c4d12b366",{"type":21,"title":1898},"Foundations of Quantum Mechanics",[1900,1917,1934,1948],{"id":1901,"data":1902,"type":25,"maxContentLevel":28,"version":25,"reviews":1906},"4f5fe3b1-5127-4b9a-a197-7a395c4a6466",{"type":25,"title":1903,"markdownContent":1904,"audioMediaId":1905},"Quantum mechanics"," ![Graph](image://2386b729-9df2-4cbb-9327-b6445aeb16bf \"A quantum computer\")\n\nQuantum mechanics is a field of physics that studies the behavior of matter and energy at the atomic and subatomic level. It was pioneered in the early 20th century by Max Planck, who proposed that energy could only be emitted or absorbed in discrete amounts, known as quanta. This revolutionary idea laid the foundation for quantum theory, which has since been used to explain phenomena such as wave-particle duality and entanglement.\n\nThe development of quantum mechanics has had far-reaching implications for our understanding of nature. For example, it explains why certain elements are stable while others decay over time; it also provides insight into how chemical reactions occur on an atomic scale. Additionally, its principles have been applied to fields such as computing and cryptography – leading to breakthroughs like quantum computers and secure communication networks.\n\nIn recent years, scientists have made great strides towards furthering our knowledge of this fascinating field: from discovering new particles like Higgs boson to exploring potential applications in medicine and engineering. As we continue to explore these uncharted territories, one thing remains clear: Quantum mechanics will remain a cornerstone of modern physics for many years to come!\n\n","5af0ab18-02d3-4cf9-b5a0-97127a53d535",[1907],{"id":1908,"data":1909,"type":51,"version":25,"maxContentLevel":28},"8dce648b-e8a0-477f-9ef3-9b4aea6fab5d",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1910,"multiChoiceCorrect":1912,"multiChoiceIncorrect":1914},[1911],"Who proposed that energy could only be emitted or absorbed in discrete amounts, known as quanta, which laid the foundation for quantum theory?",[1913],"Max Planck",[74,1915,1916],"Niels Bohr","Werner Heisenberg",{"id":1918,"data":1919,"type":25,"maxContentLevel":28,"version":25,"reviews":1923},"bc1f4cc4-960f-4523-9025-c4a7447012ae",{"type":25,"title":1920,"markdownContent":1921,"audioMediaId":1922},"Wave-particle duality"," ![Graph](image://5ff69eaf-f79e-45e1-a6f9-7fc14b775957 \"An illustration of wave-particle duality. Image: ThreePhaseAC, CC BY 4.0, via Wikimedia Commons\")\n\nWave-particle duality is a fundamental concept in quantum mechanics, which states that all particles can be considered to be both a particle or a wave. This means that the same object can behave like a wave or a particle depending on how it is observed. For example, when light passes through two slits, it behaves like a wave and produces an interference pattern; however, if we measure its position at any given time, it will appear as though the light was composed of individual particles.\n\nThis phenomenon has been demonstrated experimentally with electrons and other subatomic particles: when they are fired at two slits simultaneously, they produce an interference pattern similar to what would be expected from waves passing through the slits. However, if only one electron is sent through at a time then each electron appears to pass through either one slit or the other – behaving more like individual particles than waves.\n\nThe implications of this dual nature are far reaching: it revolutionizes the way we think about matter. Understanding the wave-particle duality has also allowed scientists to develop very powerful computers and microscopes by using this behavior to their advantage.\n\n","6f355d77-3f66-4a6a-932b-7bbc7aaf9d98",[1924],{"id":1925,"data":1926,"type":51,"version":25,"maxContentLevel":28},"f1ee7d38-218d-4ef9-8342-5c6da13f4974",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1927,"multiChoiceCorrect":1929,"multiChoiceIncorrect":1930},[1928],"What is the name of the concept which states that particles can behave as both a wave and a particle?",[1920],[1931,1932,1933],"Wave-matter duality","Particle-matter duality","Wave-particle interaction",{"id":1935,"data":1936,"type":25,"maxContentLevel":28,"version":25,"reviews":1940},"61c395ab-ff2b-4d34-bcb6-f6e06eb9104f",{"type":25,"title":1937,"markdownContent":1938,"audioMediaId":1939},"Heisenberg's uncertainty principle","Heisenberg's uncertainty principle is a fundamental concept in quantum mechanics, which states that it is impossible to simultaneously measure both the position and momentum of a particle with absolute precision. This means that the more precisely one property is known, the less precise our knowledge of the other becomes.\n\n ![Graph](image://410a955c-c9d3-4b2c-96d6-ceb7e8e37122 \"Werner Heisenberg\")\n\nHeisenberg's uncertainty principle was first proposed in 1927 by a young German scientist called Werner Heisenberg. He used a thought experiment to imagine measuring an electron using a gamma-ray microscope. He suggested that the high-energy ray used to observe the particles would introduce its own uncertainties. Although Heisenberg did not get everything correct, the uncertainty principle itself has held true. Since then, scientists have conducted numerous experiments confirming its validity and exploring its implications further. The uncertainty principle has profound implications for the way science is practiced, and must be taken into account when experiments are designed.\n","9f8317f7-1c1f-4e3a-a7fb-85e8e1945e84",[1941],{"id":1942,"data":1943,"type":51,"version":25,"maxContentLevel":28},"5a66767d-91ff-4f3f-95b5-1b2e21344f50",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1944,"multiChoiceCorrect":1946,"multiChoiceIncorrect":1947},[1945],"Who first proposed his uncertainty principle in 1927?",[1916],[74,732,72],{"id":1949,"data":1950,"type":25,"maxContentLevel":28,"version":25,"reviews":1954},"19252367-3ee2-41a6-93c3-64d855209fe0",{"type":25,"title":1951,"markdownContent":1952,"audioMediaId":1953},"The Schrödinger equation","The Schrödinger equation is a fundamental tool in quantum mechanics, used to describe the behavior of electrons and other small particles. It states that the wave function of an electron can be described by a mathematical equation, which allows us to estimate its position and momentum through probability. The wave function itself describes the probability of finding an electron in a certain place – it is essentially a ‘wave’ of probabilities that spreads out from the particle's location.\n\nThis concept has been famously illustrated with Schrodinger's cat thought experiment: if we put a cat in a box with some radioactive material, then according to quantum mechanics, until we open the box and observe what happened inside, both possibilities (the cat being alive or dead) exist simultaneously - this is known as superposition. This illustrates how observation affects reality on an atomic level; when we measure something, our observation collapses this wave-like state into one definite outcome.\n\n\n ![Graph](image://9184ae49-b198-4535-afe5-2e4af3e4babc \"The Schrodinger's cat experiment. Image: Dhatfield, CC BY-SA 3.0, via Wikimedia Commons\")\n\nThese ideas have enabled scientists to gain insight into fascinating phenomena such as entanglement and tunneling. Additionally, advances in computers allow us to apply these principles to more complex systems– potentially providing new insights into fields such as biology!\n","e5cdb320-de31-4b56-936d-a49080b81a3f",[1955],{"id":1956,"data":1957,"type":51,"version":25,"maxContentLevel":28},"a00501e5-6aa7-4f1f-b070-8cab0c0d8ca8",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":1958,"multiChoiceCorrect":1960,"multiChoiceIncorrect":1961},[1959],"What is the name of the mathematical equation used to describe the behavior of electrons and other small particles in quantum mechanics?",[1951],[1962,1963,1964],"The Heisenberg equation","The Planck equation","The Einstein equation",{"id":1966,"data":1967,"type":21,"version":25,"maxContentLevel":28,"pages":1969},"31e7f2aa-5a94-460d-b11f-072fe3f3ce23",{"type":21,"title":1968},"Applications of Quantum Mechanics",[1970,1986,2000,2015],{"id":1971,"data":1972,"type":25,"maxContentLevel":28,"version":25,"reviews":1976},"049532b9-cd1e-44c9-9dc3-ada729907bd9",{"type":25,"title":1973,"markdownContent":1974,"audioMediaId":1975},"Atomic structure"," ![Graph](image://925792d9-8d88-4dfd-8e07-788379544d65 \"A Magnesium atom. Image: Pumbaa (original work by Greg Robson), CC BY-SA 2.0 UK, via Wikimedia Commons\")\n\nAt the heart of quantum mechanics lies the concept of atomic structure. Atoms are composed of a nucleus, made up of protons and neutrons, surrounded by electrons in orbit around it. The behavior of these electrons is governed by the laws of quantum mechanics, which dictate that they can exist in multiple states at once - known as superposition. This means that an electron can be both in two places at once or have two different spins simultaneously! \n\nThe energy levels within atoms are also determined by quantum mechanics; each electron has its own discrete set of energy levels which determine how it interacts with other particles. These energy levels form what is known as an ‘electron shell’ – a series of concentric circles surrounding the nucleus where electrons reside when not interacting with other particles. Electrons move between shells depending on their interactions with other atoms and molecules, allowing for chemical reactions to occur on an atomic level.\n\nQuantum physics has enabled us to gain insight into some truly remarkable phenomena such as tunneling – where electrons can pass through barriers that would otherwise be impenetrable according to classical physics!\n\n","29385737-c997-41f0-8bbb-07fa6781df5d",[1977],{"id":1978,"data":1979,"type":51,"version":25,"maxContentLevel":28},"4abb31ca-3302-4273-bf2c-cc28e50b9714",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":1980,"binaryCorrect":1982,"binaryIncorrect":1984},[1981],"What is the name of the phenomenon where an electron can exist in multiple states at once?",[1983],"Superposition",[1985],"Entanglement",{"id":1987,"data":1988,"type":25,"maxContentLevel":28,"version":25,"reviews":1992},"787be708-f16f-4023-b03c-d3a141d989da",{"type":25,"title":1989,"markdownContent":1990,"audioMediaId":1991},"Quantum numbers and quantum states","The four quantum numbers are used to describe the properties of an atom and its electrons. These include the principal quantum number (n), which describes the energy level of an electron; angular momentum quantum number (l), which determines the shape of orbitals; magnetic quantum number (m_l) which specifies how many orbitals there are in a given shell; and spin quantum number (m_s) which describes how an electron is spinning.\n\nQuantum states provide probability distributions for systems, meaning that they can be used to predict where particles will likely be found at any given time. According to Heisenberg’s uncertainty principle, it is impossible to know both a particle's position and momentum simultaneously with absolute precision. As such, we must rely on probabilities when making predictions about atomic behavior. For example, if we know that an electron has a certain set of four quantum numbers associated with it, then we can use this information to calculate its most probable location within an atom at any given moment in time.\n\nThese same principles also allow us to understand why some elements are more stable than others – by looking at their respective sets of four quantum numbers and understanding how they interact.","041f57fe-7860-45ec-9c8e-48309fa2fd1a",[1993],{"id":1994,"data":1995,"type":51,"version":25,"maxContentLevel":28},"c51f9eec-cb64-4dc9-9c12-9823061de75e",{"type":51,"reviewType":25,"spacingBehaviour":25,"activeRecallQuestion":1996,"activeRecallAnswers":1998},[1997],"What is Heisenberg's uncertainty principle?",[1999],"It is impossible to know both a particle's position and momentum simultaneously with absolute precision.",{"id":2001,"data":2002,"type":25,"maxContentLevel":28,"version":25,"reviews":2006},"0d38418d-a053-4f64-b2c9-1c878b610502",{"type":25,"title":2003,"markdownContent":2004,"audioMediaId":2005},"The photoelectric effect and photon theory","The photoelectric effect is a phenomenon in which electrons are emitted from the surface of a material when electromagnetic radiation shines on it. This was first observed by Heinrich Hertz in 1887, and later explained by Albert Einstein in 1905. According to his theory, light consists of particles called photons that carry energy with them. When these photons hit the metal's surface, they transfer their energy to the electrons within it, causing them to be ejected from the atom.\n\n ![Graph](image://14b35321-55ad-44e1-b434-271d09d20f78 \"Heinrich Hertz\")\n\nThis discovery revolutionized our understanding of light and laid the groundwork for quantum mechanics. It showed that light behaves both as a wave and as a particle - something that had been previously thought impossible! Furthermore, this concept of ‘light quanta’ or ‘photons’ provided an explanation for phenomena such as black body radiation which could not be explained using classical physics alone.\n\nToday we know that all forms of electromagnetic radiation can be described using photon theory; radio waves, microwaves, infrared radiation etc., all consist of individual packets or 'quanta' carrying energy through space-time at speeds close to 300 million meters per second (the speed of light)!\n\n","a1916a4f-8e9b-4bf1-8267-09f0080fef4e",[2007],{"id":2008,"data":2009,"type":51,"version":25,"maxContentLevel":28},"2703ca0c-538b-44a7-a1d1-6b57efb84338",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":2010,"multiChoiceCorrect":2012,"multiChoiceIncorrect":2014},[2011],"Who first observed the photoelectric effect in 1887?",[2013],"Heinrich Hertz",[74,1591,72],{"id":2016,"data":2017,"type":25,"maxContentLevel":28,"version":25,"reviews":2021},"39920f1d-ad72-4eff-9c27-fd48ba9ba042",{"type":25,"title":2018,"markdownContent":2019,"audioMediaId":2020},"Quantum entanglement.","Quantum entanglement is a phenomenon in which two particles become linked, such that the state of one particle affects the other regardless of distance - described by Albert Einstein as ‘spooky action at a distance’. This implication of quantum mechanics was proved by John Bell in 1964. Experiments have since been conducted to verify this theory which have confirmed the validity of quantum entanglement.\n\n ![Graph](image://501ce248-f266-4f2d-b077-1f8c89ec96f1 \"Alain Aspect. Image: The Royal Society, CC BY-SA 3.0, via Wikimedia Commons\")\n\nOne such experiment was conducted by Alain Aspect in 1981. In this experiment, photons were sent through polarizers and their polarization states were measured; it was found that when one photon changed its polarization state, so did the other - even though they had been separated by 12 meters. This provided strong evidence for quantum entanglement and has since been replicated numerous times with similar results.\n\nThe potential applications of quantum entanglement are vast; from secure communication networks to ultra-precise clocks and sensors. It could also be used as a powerful tool for computing due to its ability to process information faster than traditional computers can manage – something known as 'quantum computing'. Ultimately, further research into this field may lead us towards new discoveries about our universe that we never thought possible before!","989d178c-9b72-4b69-a717-60e66c2ef43c",[2022],{"id":2023,"data":2024,"type":51,"version":25,"maxContentLevel":28},"913fd15c-77d4-4383-aa14-ab1d2387c637",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":2025,"binaryCorrect":2027,"binaryIncorrect":2029},[2026],"In which year did John Bell prove the theory of quantum entanglement?",[2028],"1964",[2030],"1981",{"id":2032,"data":2033,"type":27,"maxContentLevel":28,"version":25,"orbs":2036},"da09aaf4-68f5-41d9-aef1-4c376d8b5abf",{"type":27,"title":2034,"tagline":2035},"Astrophysics","The physics of the stars.",[2037,2134,2188],{"id":2038,"data":2039,"type":21,"version":25,"maxContentLevel":28,"pages":2041},"790b1a88-6c1c-470d-901c-6dcb5714995e",{"type":21,"title":2040},"The Universe and Its Components",[2042,2058,2084,2098,2116],{"id":2043,"data":2044,"type":25,"maxContentLevel":28,"version":25,"reviews":2048},"a0e5aa01-d346-4c74-a1e5-c09cb7ab4915",{"type":25,"title":2045,"markdownContent":2046,"audioMediaId":2047},"The study of the universe","Astrophysics is the study of the universe, from its smallest components to its largest structures. It seeks to understand phenomena such as star formation and evolution, planetary systems, galaxies, and cosmology. Astrophysics also studies how matter behaves in extreme conditions like those found in neutron stars or black holes.\n\nThe life cycle of a star is one example of an astrophysical phenomenon that has been studied for centuries. Stars are born when clouds of gas and dust collapse under their own gravity; they then shine brightly for millions or billions of years before eventually dying out as white dwarfs or supernova explosions. Planets form around stars through accretion processes, while asteroids and comets orbit them due to gravitational forces. All these objects interact with each other in complex ways that can be explored using astrophysical models and simulations.\n\n\n ![Graph](image://9791447e-1bc9-4a95-a781-93c432785cf6 \"Neutron stars. Image: NOIRLab/NSF/AURA/J. da Silva/Spaceengine, CC BY 4.0, via Wikimedia Commons\")\n\nThe importance of astrophysics lies not only in understanding our place within the universe but also in providing us with valuable insights into our own planet's history and future development - from climate change to energy production technologies based on nuclear fusion reactions similar to those occurring inside stars.\n","351a9424-ca14-4d74-af4f-e9af21d92e68",[2049],{"id":2050,"data":2051,"type":51,"version":25,"maxContentLevel":28},"e88c8d64-de7d-44d4-8ae3-f5402835ad36",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":2052,"binaryCorrect":2054,"binaryIncorrect":2056},[2053],"What is the process by which planets form around stars?",[2055],"Accretion",[2057],"Erosion",{"id":2059,"data":2060,"type":25,"maxContentLevel":28,"version":25,"reviews":2064},"1cdb2dae-3e72-4e53-b635-60128acff9d5",{"type":25,"title":2061,"markdownContent":2062,"audioMediaId":2063},"The solar system","\n ![Graph](image://8f6c924a-309c-4a94-ba41-33a24deba7ab \"The solar system\")\n\nThe solar system is a fascinating example of astrophysics in action. It consists of the sun and its orbiting bodies: eight planets and their moons, dwarf planets such as Pluto and Ceres, asteroids, comets and other small bodies.\n\nPlanetary formation occurs when dust particles coalesce into larger clumps due to gravitational attraction; this process can take millions or even billions of years depending on the size of the object being formed. The planets then move along elliptical paths around the sun at different speeds according to Kepler's laws of planetary motion. For instance, Mercury has a highly eccentric orbit which takes it 88 days to complete one revolution while Neptune takes 165 years!\n\nIn addition to its planets, our solar system also contains many smaller bodies like asteroids and comets which have been studied extensively by astronomers over centuries. These objects provide valuable insights into how our own planet was formed 4 billion years ago from similar materials found in space today. They also offer clues about potential threats posed by near-Earth objects (NEOs) such as meteorites or comets that could collide with Earth if they come too close!\n","08c2236d-669e-4b7d-b1eb-5291267f7ec9",[2065,2073],{"id":2066,"data":2067,"type":51,"version":25,"maxContentLevel":28},"734a168c-d48e-4584-84bd-a79826e424ce",{"type":51,"reviewType":132,"spacingBehaviour":25,"clozeQuestion":2068,"clozeWords":2070},[2069],"Astronomers study asteroids and comets to gain insights into our solar system.",[2071,2072],"asteroids","comets",{"id":2074,"data":2075,"type":51,"version":25,"maxContentLevel":28},"81bb3119-6c94-43cc-b2d3-9a44051587ea",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":2076,"multiChoiceCorrect":2078,"multiChoiceIncorrect":2080},[2077],"According to Kepler's laws of planetary motion, how long does it take Neptune to complete one revolution around the sun?",[2079],"165 years",[2081,2082,2083],"88 days","365 days","24 hours",{"id":2085,"data":2086,"type":25,"maxContentLevel":28,"version":25,"reviews":2090},"1be2e1fa-dd99-4165-ac24-836ecb5db011",{"type":25,"title":2087,"markdownContent":2088,"audioMediaId":2089},"The formation of stars"," ![Graph](image://17769de0-8399-45e6-872f-a44e534d96c0 \"A constellation of stars\")\n\nThe formation of stars is a complex process that has been studied for centuries. It begins within a dense region of a nebula - an interstellar cloud of gas and dust - which collapses under its own gravity to form a protostar. As this protostar continues to collapse, it heats up until nuclear fusion reactions begin taking place at its core, releasing energy in the form of light and heat. This marks the birth of a star!\n\nThe timeline for star formation can vary greatly depending on size; stars like our sun take around 50 million years to fully form. On the other hand, very large stars form much faster - a very high mass protostar might take only a million years to collapse into a star. During their formation, they will also grow brighter as their cores become hotter and denser due to gravitational compression. Eventually they reach equilibrium where nuclear fusion reactions balance out gravitational contraction, allowing them to shine steadily for hundreds of thousands, millions or even billions of years before eventually dying out as white dwarfs or supernovae explosions.\n\n","db910558-706c-48b5-ae45-fc182e269346",[2091],{"id":2092,"data":2093,"type":51,"version":25,"maxContentLevel":28},"d9172d7a-0e9f-4204-9ce0-aad0437c1f7b",{"type":51,"reviewType":25,"spacingBehaviour":25,"activeRecallQuestion":2094,"activeRecallAnswers":2096},[2095],"What is the timeline for stars like our sun to form?",[2097],"50 million years",{"id":2099,"data":2100,"type":25,"maxContentLevel":28,"version":25,"reviews":2104},"eaa50786-7de9-4cb3-aaa6-99736ee60e7c",{"type":25,"title":2101,"markdownContent":2102,"audioMediaId":2103},"Stellar evolution","The lifetime of a star is determined by its mass, with larger stars burning through their fuel much faster than smaller ones. For example, our sun has a lifespan of around 10 billion years while more massive stars may only live for a few million years before they die out. As the star runs out of fuel and begins to cool down, it will expand into what is known as a red giant before eventually collapsing in on itself and becoming either a white dwarf or neutron star depending on its mass.\n\nMore massive stars can even go one step further and explode in an incredibly powerful supernova event that releases vast amounts of energy into space! The remnants from this explosion are then compressed so tightly that they form incredibly dense neutron stars or black holes.\n\nDuring their lifetimes, stars produce elements such as carbon and oxygen through nucleosynthesis processes which are then spread throughout the universe when they die. Interestingly enough, nearly all elements heavier than hydrogen were created this way! This means that much of the matter on Earth originates in ancient stars – making us all stardust in one way or another.","deb25a58-1725-4da7-8ea7-cab1011e3419",[2105],{"id":2106,"data":2107,"type":51,"version":25,"maxContentLevel":28},"649d50a4-d45b-4017-8ad0-237032660d48",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":2108,"multiChoiceCorrect":2110,"multiChoiceIncorrect":2112},[2109],"What is the result of a star running out of fuel and cooling down?",[2111],"A red giant",[2113,2114,2115],"A white dwarf","A neutron star","A black hole",{"id":2117,"data":2118,"type":25,"maxContentLevel":28,"version":25,"reviews":2122},"7d926878-12c3-44bb-9450-aa26f5565553",{"type":25,"title":2119,"markdownContent":2120,"audioMediaId":2121},"Black holes"," ![Graph](image://29b51e26-2989-445f-84f8-d9c7f03b8dbe \"The Milky Way galaxy. Image: Pablo Carlos Budassi, CC BY-SA 4.0, via Wikimedia Commons\")\n\nBlack holes are some of the most mysterious and fascinating objects in the universe. They are regions of space where gravity is so strong that nothing, not even light, can escape its pull. These incredibly dense objects can form when a star runs out of fuel and collapses in on itself due to its own gravity. The more massive the star was before it collapsed, the larger and denser the resulting black hole will be.\n\nThe Milky Way galaxy contains a supermassive black hole at its centre - with a diameter of around 14.6 million miles (23.5 million kilometers)! Other galaxies also contain these giant structures which can have masses up to billions of solar masses – making them some of the largest known objects in existence! It’s thought that these supermassive black holes may have played an important role in shaping their host galaxies over time by consuming material from around them or ejecting powerful jets into interstellar space.\n\n","11176337-b29b-4337-8728-55bed0f96d32",[2123],{"id":2124,"data":2125,"type":51,"version":25,"maxContentLevel":28},"8fd24a7d-9ed8-4551-8d04-5f1cd891f682",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":2126,"multiChoiceCorrect":2128,"multiChoiceIncorrect":2130},[2127],"What is the diameter of the supermassive black hole at the centre of the Milky Way galaxy?",[2129],"14.6 million miles (23.5 million kilometers)",[2131,2132,2133],"6.2 million miles (10 million kilometers)","9.8 million miles (15.8 million kilometers)","12.4 million miles (20 million kilometers)",{"id":2135,"data":2136,"type":21,"version":25,"maxContentLevel":28,"pages":2138},"ec52d5db-7059-43c6-92ab-0ad941c92d66",{"type":21,"title":2137},"The Structure of Galaxies",[2139,2157,2172],{"id":2140,"data":2141,"type":25,"maxContentLevel":28,"version":25,"reviews":2145},"cfbeee53-cec0-43f7-904c-15ce97ad6e54",{"type":25,"title":2142,"markdownContent":2143,"audioMediaId":2144},"Galaxies and the Milky Way","\nGalaxies are vast collections of stars, gas and dust held together by gravity. They come in a variety of shapes, from spiral to elliptical, depending on how they form and merge with each other over time. Our own Milky Way is an example of a barred spiral galaxy – it has a central bar-shaped structure surrounded by two major arms that wrap around the center like a pinwheel. It's estimated to be about 13 billion years old and is estimated to contain between 100 billion and 400 billion stars!\n\nAt the very heart of our galaxy lies Sagittarius A*, or Sgr A* for short - an incredibly dense supermassive black hole with an estimated mass 4 million times greater than our sun! This giant object is thought to have played an important role in shaping the Milky Way over its lifetime by consuming material from around it or ejecting powerful jets into interstellar space. In addition, astronomers believe that this supermassive black hole may also be responsible for some mysterious phenomena such as high-energy gamma ray bursts detected near its location.\n\n","e4686023-5272-48c9-9bcc-8a0a3742fd9f",[2146],{"id":2147,"data":2148,"type":51,"version":25,"maxContentLevel":28},"b8cbd0a3-c4dc-4c99-95f1-76744fc1e689",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":2149,"multiChoiceCorrect":2151,"multiChoiceIncorrect":2153},[2150],"What is the estimated mass of the supermassive black hole at the heart of the Milky Way?",[2152],"4 million times greater than our sun",[2154,2155,2156],"100 billion times greater than our sun","400 billion times greater than our sun","13 billion times greater than our sun",{"id":2158,"data":2159,"type":25,"maxContentLevel":28,"version":25,"reviews":2163},"1789af19-51b5-479a-b06c-05061b92c393",{"type":25,"title":2160,"markdownContent":2161,"audioMediaId":2162},"The expanding universe","The idea of an expanding universe was first proposed by Edwin Hubble in 1929, when he observed that the light from distant stars was red-shifted due to the Doppler effect. This meant that these stars were moving away from us at a rapid rate, suggesting that the universe itself is growing larger over time.\n\nToday we understand this phenomenon as part of a much bigger picture - one where space itself is stretching and expanding along with all matter within it. The implications of this are far reaching; for example, it suggests that our universe had a beginning (the Big Bang) and might continue to expand forever into an ever-cooling state known as ‘heat death’.\n \nOur current understanding of the expanding universe has been greatly aided by advances in technology such as powerful telescopes which allow us to observe objects billions of light years away, giving us unprecedented insight into how our cosmos works on both small and large scales.","d8dc4bdf-84a2-4633-afc3-ce8e08cbdd28",[2164],{"id":2165,"data":2166,"type":51,"version":25,"maxContentLevel":28},"384f6153-5bf6-4e9e-a2f0-66ce097d4b86",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":2167,"binaryCorrect":2169,"binaryIncorrect":2171},[2168],"Who proposed the idea of an expanding universe?",[2170],"Edwin Hubble",[1913],{"id":2173,"data":2174,"type":25,"maxContentLevel":28,"version":25,"reviews":2178},"74f91d7c-fe03-4653-a95d-d9612da1e066",{"type":25,"title":2175,"markdownContent":2176,"audioMediaId":2177},"Dark matter and dark energy","Dark matter and dark energy are two mysterious components of the universe that have been theorised to explain its structure and expansion. Dark matter is believed to make up around 85% of all mass in the universe, yet it cannot be seen directly as it does not emit or absorb light. It can only be detected through its gravitational effects on other objects such as galaxies, which appear to rotate faster than they should given their visible mass.\n\n ![Graph](image://cb895135-cab1-4785-8dbc-6d195590a679 \"Dark energy\")\n\nDark energy is an even more enigmatic force thought to account for around 68% of the universe. This mysterious form of energy appears to be pushing galaxies away from each other at an ever-increasing rate, causing the expansion of space itself. Scientists believe this could eventually lead to a ‘Big Rip’ where all matter will be torn apart by the expanding fabric of space-time!\n\nThe exact nature and origin of these two phenomena remain largely unknown but scientists continue to study them using powerful telescopes and simulations in order to gain further insight into how they shape our cosmos.\n","97be84ed-bed4-4585-8ccc-01c89cf16df7",[2179],{"id":2180,"data":2181,"type":51,"version":25,"maxContentLevel":28},"86572c49-5acb-4da4-ac5f-d8c8a2d6fa8c",{"type":51,"reviewType":21,"spacingBehaviour":25,"binaryQuestion":2182,"binaryCorrect":2184,"binaryIncorrect":2186},[2183],"What percentage of matter in the universe is believed to be made up of dark matter?",[2185],"85%",[2187],"68%",{"id":2189,"data":2190,"type":21,"version":25,"maxContentLevel":28,"pages":2192},"54dd2350-84db-478d-af1d-b61d0539f3f0",{"type":21,"title":2191},"Theories of the Universe",[2193,2211],{"id":2194,"data":2195,"type":25,"maxContentLevel":28,"version":25,"reviews":2199},"2a3a00d1-9bd8-4006-a225-59486a6a3815",{"type":25,"title":2196,"markdownContent":2197,"audioMediaId":2198},"The big bang theory","The Big Bang Theory is the prevailing cosmological model for how the universe began. It states that at some point in time, all matter and energy were concentrated into a single infinitely dense point known as a singularity. This then exploded outward in an event known as the Big Bang, creating space and time itself.\n\nThis initial expansion was incredibly rapid, starting with what is known as the Planck epoch - a period of 10^-43 seconds after which quantum effects become important. Immediately after this epoch it is believed that inflation occurred; an exponential expansion of space possibly driven by dark energy.\n\nEvidence for this theory comes from observations such as cosmic microwave background radiation (CMB), which can be detected across vast distances and appears to be uniform throughout our universe - suggesting it originated from one single source at some point in time. Additionally, we observe that galaxies are moving away from each other with increasing speed due to universal expansion - another indication of a past big bang event! Finally, abundances of elements like hydrogen and helium found throughout our cosmos match predictions made by models based on the big bang theory perfectly - further strengthening the theory!","0ed44a0b-13b0-41d3-af0b-fb1d42d6ea30",[2200],{"id":2201,"data":2202,"type":51,"version":25,"maxContentLevel":28},"f49fe645-d10c-4542-a24a-c780bc95410f",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":2203,"multiChoiceCorrect":2205,"multiChoiceIncorrect":2207},[2204],"What is the name of the prevailing cosmological model for how the universe began?",[2206],"The Big Bang Theory",[2208,2209,2210],"The Big Crunch Theory","The Big Bounce Theory","The Big Expansion Theory",{"id":2212,"data":2213,"type":25,"maxContentLevel":28,"version":25,"reviews":2217},"71e8f45a-8c0e-4c6a-a14a-63ba3dbb30d8",{"type":25,"title":2214,"markdownContent":2215,"audioMediaId":2216},"The fate of the universe","The fate of the universe is a topic that has been debated for centuries, and there are several theories as to what may happen. One such theory is the Big Crunch, which suggests that due to gravity, all matter in the universe will eventually be pulled back together into one single point - much like how it began with the Big Bang. This would cause space-time itself to collapse and end in an infinitely dense singularity.\n\nAnother possible outcome is known as The Big Rip, where the expansion of the universe continues to increase until it becomes so strong that it tears apart galaxies and stars themselves! This could occur billions of years from now, but if true would mean our universe will ultimately come undone at its very seams.\n\nA third theory, sometimes known as the big chill, suggests we may be heading towards a state known as 'heat death' where there is no available energy left in the universe! Whatever happens next remains unknown; only time will tell what lies ahead for our ever-expanding cosmos!","c34d87a2-bb30-4798-9a52-f12cbd0088d1",[2218],{"id":2219,"data":2220,"type":51,"version":25,"maxContentLevel":28},"57833277-e6be-440f-a8fa-fffa6b77e295",{"type":51,"reviewType":28,"spacingBehaviour":25,"multiChoiceQuestion":2221,"multiChoiceCorrect":2223,"multiChoiceIncorrect":2225},[2222],"What is the name of the theory which suggests that gravity will pull all matter back together into one point?",[2224],"Big Crunch",[2226,2227,2228],"Big Rip","Big Freeze","Big Chill",{"left":4,"top":4,"width":2230,"height":2230,"rotate":4,"vFlip":6,"hFlip":6,"body":2231},24,"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"m9 18l6-6l-6-6\"/>",{"left":4,"top":4,"width":2230,"height":2230,"rotate":4,"vFlip":6,"hFlip":6,"body":2233},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M12.586 2.586A2 2 0 0 0 11.172 2H4a2 2 0 0 0-2 2v7.172a2 2 0 0 0 .586 1.414l8.704 8.704a2.426 2.426 0 0 0 3.42 0l6.58-6.58a2.426 2.426 0 0 0 0-3.42z\"/>\u003Ccircle cx=\"7.5\" cy=\"7.5\" r=\".5\" fill=\"currentColor\"/>\u003C/g>",1778179493821]