WEBVTT 00:00:00.500 --> 00:00:05.490 [ Music ] 00:00:08.040 --> 00:00:11.380 >> If you have ever been out in the intense sun too long 00:00:11.380 --> 00:00:15.340 and received a sunburn, you know how powerful the sun's light 00:00:15.340 --> 00:00:16.950 energy can be. 00:00:16.950 --> 00:00:21.870 Sunlight is a form of energy, referred to as radiation. 00:00:21.870 --> 00:00:24.110 It travels in waves. 00:00:24.110 --> 00:00:28.700 The distance between the top or crest of one wave and the crest 00:00:28.700 --> 00:00:32.470 of the next wave is a wavelength of light. 00:00:32.470 --> 00:00:36.680 Sunlight, also called white light, is a mixture 00:00:36.680 --> 00:00:38.660 of all visible wavelengths, 00:00:38.660 --> 00:00:42.050 as well as many wavelengths we can't see. 00:00:42.050 --> 00:00:45.120 When white light passes through a prism, 00:00:45.120 --> 00:00:48.600 it's bent by different amounts, spreading out the light 00:00:48.600 --> 00:00:52.100 into a spectrum we see as different colors. 00:00:52.100 --> 00:00:55.060 The colors appear in order of their wavelengths, 00:00:55.060 --> 00:00:59.740 with the shortest wavelength, violet, at one end, and red, 00:00:59.740 --> 00:01:03.550 the longest wavelength, at the other end of the spectrum. 00:01:03.550 --> 00:01:07.810 While light behaves as waves, it also acts as if it were made 00:01:07.810 --> 00:01:11.270 up of energy particles called photons. 00:01:11.270 --> 00:01:13.700 The shorter the wavelength of light, 00:01:13.700 --> 00:01:17.160 the more energy a photon carries. 00:01:17.160 --> 00:01:19.960 Certain substances, called pigments, 00:01:19.960 --> 00:01:25.070 are capable of absorbing photons and their energy. 00:01:25.070 --> 00:01:28.980 Specific types of pigments absorb certain wavelengths 00:01:28.980 --> 00:01:31.900 of light and reflect others. 00:01:31.900 --> 00:01:34.180 The different wavelengths of light absorbed 00:01:34.180 --> 00:01:39.200 by a particular pigment make up its absorption spectrum. 00:01:39.200 --> 00:01:44.210 Two general types of pigments, chlorophylls and carotenoids, 00:01:44.210 --> 00:01:46.510 are found in green plants. 00:01:46.510 --> 00:01:48.520 The pigments chlorophyll a 00:01:48.520 --> 00:01:54.010 and chlorophyll b absorb violet blue and red light. 00:01:54.010 --> 00:01:57.070 Carotenoids absorb light primarily 00:01:57.070 --> 00:01:59.640 in the violet, blue range. 00:01:59.640 --> 00:02:01.890 You decide. 00:02:03.690 --> 00:02:06.510 Why do plants look green? 00:02:06.510 --> 00:02:12.890 [ Music ] 00:02:12.890 --> 00:02:16.510 Chlorophylls and carotenoids do not absorb light 00:02:16.510 --> 00:02:18.590 in the green part of the spectrum. 00:02:18.590 --> 00:02:21.710 Instead, they reflect green light. 00:02:21.710 --> 00:02:25.190 Consequently, most plants appear green.