Yellow Sun and Green Plants ``` Isaak Status: Grade: 4-5 Location: Outside U.S. Country: New Zealand Date: Winter 2011-2012 ``` Question: Why does plants show green and not yellow because the sun is yellow? Replies: NOTE: The first answer assumes you are looking at the suggested web site. Isaak br> Radio and TV signals are a form of electro-magnetic waves. Light is also a form of electro-magnetic waves. The difference between radio and TV signals and light is their frequency. Here is a diagram from Wikipedia (http://en.wikipedia.org/wiki/Frequency) of signals of different frequencies: The top signal is a low frequency wave, the bottom signal is a high frequency wave. Light frequencies are much, much higher than radio and TV frequencies. Here is a frequency chart of the visible light spectrum from the same Wikipedia article demonstrating that light is a far higher frequency than radio and TV signals: br> As shown in this visible light spectrum chart, specific light colors have different frequencies. Please also notice that the higher the frequency, the lower the wavelength; and The higher the wavelength, the lower the frequency (they are the reciprocal of each other) Here is a list (from http://en.wikipedia.org/wiki/Visible_spectrum) of colors and their frequencies: (THz and nm are quantities of frequency and wavelength) Color Frequency Wavelength violet 668–789 THz 380–450 nm blue 631–668 THz 450–475 nm cyan 606–630 THz 476–495 nm green 526–606 THz 495–570 nm yellow 508–526 THz 570–590 nm orange 484–508 THz 590–620 nm red 400–484 THz 620–750 nm violet 668–789 THz 380–450 nm blue 631–668 THz 450–475 nm cyan 606–630 THz 476–495 nm green 526–606 THz 495–570 nm yellow 508–526 THz 570–590 nm orange 484–508 THz 590–620 nm red 400–484 THz 620–750 nm Sun light is really white light which is the combination of all light frequencies. The reason why plants are green is because the plants absorb the light frequency of all colors of the colors EXCEPT green. So the green light is reflected back by the plants instead of being absorbed which is why we seen plants as the color green. Sincere regards, Mike Stewart The sun emits radiation that is made up of all the colors of the rainbow. The sun tends to look yellow because the earth's atmosphere filters and scatters some of the other colors. Any color that gets through blends together and is read by our eyes as yellow (we have little receivers that interpret color for us)! Plants can use a very small fraction of the color that gets through for photosynthesis. One color they really can't use is green. This is reflected back as the green color we are all used to. Dr. Tim Durham Undergraduate Studies & University Colloquium Department of Biological Sciences Florida Gulf Coast University Click here to return to the Botany Archives

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