As you probably know... a given color of light can generally, be described by one number (e.g., the frequency of its wave length).

The color white, however, has no associated frequency; it is composed of equal amounts of all the (visible) frequencies of light. Black, of course, is the absence of light. And various shades of grey are generally composed of various intensities of white (as you lower the overall intensity of white, the grey gets darker and approaches black).

The question is: why is light (optically) additive? More specifically, why is it that when we add Red and Green together we get Yellow; Green and Blue together, we get Cyan; Red, Green, and Blue together, we get white?

(Please don't confuse this with the subtractive quality of pigments/paints, where as we add more colors, particularly more of the primary colors red, yellow, and blue, we approach black.)

Could we use three (or more) different colors and achieve the same result?

Since light is a wave, this probably results from the addition of the corresponding waves.  This also takes into consideration that light doesn't just occur in one plane.

Adding a wave that has 350nm wavelength (which means the frequency is 3x10^8/350nm) with one that has 600nm (which means the frequency is 3x10^8/600nm) would probably result in a third wave, at a different frequency.  This frequency can then yield a wavelength of the resulting wave by dividing the speed of light by it.  This is the resulting color.

In the case of white, the reason why there's probably no wavelength associated with it comes from the fact that it is an addition of all waves of light.  It probably is formed by all colors, all on different planes perpendicular to the travel of light.  Therefore, if you add them all up, you get a straight line, BUT if you use a prism you can separate the light planes.

Or something.

Posted by Alexis on 2005-12-07 16:29:34