full transcript

From the Ted Talk by Colm Kelleher: What is color?

Unscramble the Blue Letters

One of the most striking properties about life is that it has color. To understand the phenomenon of color, it hleps to think about light as a wave. But, before we get to that, let's talk a little bit about waves in general. ignmiae you're sitting on a boat on the ocean watching a cork bob up and down in the water. The first thing you ntcoie about the motion is that it repeats itself. The cork traces the same path over and over again... up and down, up and down. This repetitive or periodic motion is crestarictiahc of wvaes. Then you notice something else... using a spawtctoh, you measure the time it takes for the pceie of cork to go over its highest position down to its lwesot and then back up again. Suppose this tekas two seconds. To use the physics jargon, you've measured the period of the waves that cork is bobbing on. That is, how long it takes a wave to go through its full rgnae of motion once. The same information can be expressed in a different way by calculating the wave's frequency. Frequency, as the name suggest, tlels you how frequent the waves are. That is, how many of them go by in one second. If you know how many soecnds one full wave takes, then it's easy to work out how many waves go by in one second. In this case, since each wave takes 2 seconds, the frequency is 0.5 waves per second. So enough about bobbing corks... What about light and color? If light is a wave, then it must have a frequency. Right? Well... yes, it does. And it turns out that we already have a name for the frequency of the light that our eyes detect. It's called color. That's right. Color is nothing more than a mesaure of how qlkiucy the light waves are winavg. If our eyes were quick enough, we might be able to observe this periodic motion directly, like we can with the cork and the ocean. But the fencrqeuy of the lhigt we see is so high, it waves up and down about 400 million million times a second, that we can't polibssy see it as a wave. But we can tell, by looking at its color, what its frequency is. The lowest frequency light that we can see is red and the highest frequency is plprue. In between all the other frequencies form a continuous band of color, called the visible spectrum. So, what if you had a yellow pencil snttiig on your desk? Well, the sun emits all colors of light, so light of all colors is hitting your pencil. The pencil looks yleolw because it reflects yellow light more than it reflects the other colors. What happens to the blue, purple and red light? They get absorbed and the energy they are cyrirnag is turned into heat. It is slmiiar with objects of other colors. Blue things reflect blue light, red things reflect red light and so on. White objects reflect all cloros of light, while black things do exactly the opposite and absorb at all frequencies. This - by the way - is why it's uncomfortable to wear your favorite Metallica t-shirt on a snuny day.

Open Cloze

One of the most striking properties about life is that it has color. To understand the phenomenon of color, it _____ to think about light as a wave. But, before we get to that, let's talk a little bit about waves in general. _______ you're sitting on a boat on the ocean watching a cork bob up and down in the water. The first thing you ______ about the motion is that it repeats itself. The cork traces the same path over and over again... up and down, up and down. This repetitive or periodic motion is ______________ of _____. Then you notice something else... using a _________, you measure the time it takes for the _____ of cork to go over its highest position down to its ______ and then back up again. Suppose this _____ two seconds. To use the physics jargon, you've measured the period of the waves that cork is bobbing on. That is, how long it takes a wave to go through its full _____ of motion once. The same information can be expressed in a different way by calculating the wave's frequency. Frequency, as the name suggest, _____ you how frequent the waves are. That is, how many of them go by in one second. If you know how many _______ one full wave takes, then it's easy to work out how many waves go by in one second. In this case, since each wave takes 2 seconds, the frequency is 0.5 waves per second. So enough about bobbing corks... What about light and color? If light is a wave, then it must have a frequency. Right? Well... yes, it does. And it turns out that we already have a name for the frequency of the light that our eyes detect. It's called color. That's right. Color is nothing more than a _______ of how _______ the light waves are ______. If our eyes were quick enough, we might be able to observe this periodic motion directly, like we can with the cork and the ocean. But the _________ of the _____ we see is so high, it waves up and down about 400 million million times a second, that we can't ________ see it as a wave. But we can tell, by looking at its color, what its frequency is. The lowest frequency light that we can see is red and the highest frequency is ______. In between all the other frequencies form a continuous band of color, called the visible spectrum. So, what if you had a yellow pencil _______ on your desk? Well, the sun emits all colors of light, so light of all colors is hitting your pencil. The pencil looks ______ because it reflects yellow light more than it reflects the other colors. What happens to the blue, purple and red light? They get absorbed and the energy they are ________ is turned into heat. It is _______ with objects of other colors. Blue things reflect blue light, red things reflect red light and so on. White objects reflect all ______ of light, while black things do exactly the opposite and absorb at all frequencies. This - by the way - is why it's uncomfortable to wear your favorite Metallica t-shirt on a _____ day.

Solution

  1. helps
  2. waves
  3. takes
  4. measure
  5. purple
  6. range
  7. stopwatch
  8. seconds
  9. quickly
  10. notice
  11. sunny
  12. frequency
  13. yellow
  14. imagine
  15. possibly
  16. characteristic
  17. lowest
  18. light
  19. similar
  20. piece
  21. sitting
  22. tells
  23. colors
  24. carrying
  25. waving

Original Text

One of the most striking properties about life is that it has color. To understand the phenomenon of color, it helps to think about light as a wave. But, before we get to that, let's talk a little bit about waves in general. Imagine you're sitting on a boat on the ocean watching a cork bob up and down in the water. The first thing you notice about the motion is that it repeats itself. The cork traces the same path over and over again... up and down, up and down. This repetitive or periodic motion is characteristic of waves. Then you notice something else... using a stopwatch, you measure the time it takes for the piece of cork to go over its highest position down to its lowest and then back up again. Suppose this takes two seconds. To use the physics jargon, you've measured the period of the waves that cork is bobbing on. That is, how long it takes a wave to go through its full range of motion once. The same information can be expressed in a different way by calculating the wave's frequency. Frequency, as the name suggest, tells you how frequent the waves are. That is, how many of them go by in one second. If you know how many seconds one full wave takes, then it's easy to work out how many waves go by in one second. In this case, since each wave takes 2 seconds, the frequency is 0.5 waves per second. So enough about bobbing corks... What about light and color? If light is a wave, then it must have a frequency. Right? Well... yes, it does. And it turns out that we already have a name for the frequency of the light that our eyes detect. It's called color. That's right. Color is nothing more than a measure of how quickly the light waves are waving. If our eyes were quick enough, we might be able to observe this periodic motion directly, like we can with the cork and the ocean. But the frequency of the light we see is so high, it waves up and down about 400 million million times a second, that we can't possibly see it as a wave. But we can tell, by looking at its color, what its frequency is. The lowest frequency light that we can see is red and the highest frequency is purple. In between all the other frequencies form a continuous band of color, called the visible spectrum. So, what if you had a yellow pencil sitting on your desk? Well, the sun emits all colors of light, so light of all colors is hitting your pencil. The pencil looks yellow because it reflects yellow light more than it reflects the other colors. What happens to the blue, purple and red light? They get absorbed and the energy they are carrying is turned into heat. It is similar with objects of other colors. Blue things reflect blue light, red things reflect red light and so on. White objects reflect all colors of light, while black things do exactly the opposite and absorb at all frequencies. This - by the way - is why it's uncomfortable to wear your favorite Metallica t-shirt on a sunny day.

Frequently Occurring Word Combinations

ngrams of length 2

collocation frequency
periodic motion 2

Important Words

  1. absorb
  2. absorbed
  3. band
  4. bit
  5. black
  6. blue
  7. boat
  8. bob
  9. bobbing
  10. calculating
  11. called
  12. carrying
  13. case
  14. characteristic
  15. color
  16. colors
  17. continuous
  18. cork
  19. corks
  20. day
  21. desk
  22. detect
  23. easy
  24. emits
  25. energy
  26. expressed
  27. eyes
  28. favorite
  29. form
  30. frequencies
  31. frequency
  32. frequent
  33. full
  34. general
  35. heat
  36. helps
  37. high
  38. highest
  39. hitting
  40. imagine
  41. information
  42. jargon
  43. life
  44. light
  45. long
  46. lowest
  47. measure
  48. measured
  49. metallica
  50. million
  51. motion
  52. notice
  53. objects
  54. observe
  55. ocean
  56. path
  57. pencil
  58. period
  59. periodic
  60. phenomenon
  61. physics
  62. piece
  63. position
  64. possibly
  65. properties
  66. purple
  67. quick
  68. quickly
  69. range
  70. red
  71. reflect
  72. reflects
  73. repeats
  74. repetitive
  75. seconds
  76. similar
  77. sitting
  78. spectrum
  79. stopwatch
  80. striking
  81. suggest
  82. sun
  83. sunny
  84. suppose
  85. takes
  86. talk
  87. tells
  88. time
  89. times
  90. traces
  91. turned
  92. turns
  93. uncomfortable
  94. understand
  95. visible
  96. watching
  97. water
  98. wave
  99. waves
  100. waving
  101. wear
  102. white
  103. work
  104. yellow