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Q & A: colors and wavelengths

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Most recent answer: 10/22/2007
Q:
I have been doing some studying on light, wavelenghts, and prisms, and I understand that visible white light is the combination of all the colors of light. (red, yellow, etc.) However, my specific question is this: what actually causes the actual "color" of light and their wavelenghts? I know that red is the faster or shorter wavelenghts, but what actually throws off the colors which are seen in a prism for instance? Why is the red part of the wavelenght red in the prism or rainbow and not green or any other color? I think this is happening on a very atomic level.
- Alexa (age 15 years)
Daytona Beach, FL.
A:
First of all you have to distinguish between the human perception of  'red' or 'green' light and the scientific measurable properties of what we call 'red' or 'green'. 

Visible light of all colors has an associated wavelength and a frequency, related by
lambda = c / f   where lambda is the wavelength, c  is the speed of light, and f is the frequency. These properties are measurable in the laboratory.

 The human ability to distinguish one 'color' or wavelength has to do with the properties of the eye.  There are several types of light sensing cone photoreceptors in the retina that are sensitive to different wavelengths.   The brain receives information from these three types and then figures out what the color is.

What we perceive as 'red' tends to have longer wavelengths than that of 'green'.  So it tends to excite one type of photoreceptor more than the others.   The brain decides "It's Red"

Look at the Wikipedia site  for more information.

LeeH

p.s.- and come back with a follow-up if more discussion is needed.  Mike W.




(published on 10/22/2007)

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