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?

(In reply to easy on the eye by john)

Not really in reply to this comment, but to extend...    in a way...

Two wavelengths of light won't add to a new wave, like John said, it's really the brain that adds them together.  For example if there was red+green light around, you would see red+green, and interpret it as yellow.  The reason for this is that if there was actual yellow light, you would also see it as red+green and interpret it as yellow.

Also, I suppose light is an exception to most energy waves in the way that 2 waves won't add to each other and make a wave with greater magnitude.  It's not like sound where if you make two waves slightly out of tune, the magnitude would oscillate.

Well, I think that demonstrated my (lack of) knowledge of physics well.

Posted by Tristan on 2004-03-05 17:43:32