Can we consider recombination process of different light colors a linear system/phenomenon? Like, when you shed two different light sources for example, a blue light and a yellow light on a surface or recombine them through a prism , the resultant light would be green which has a different frequency that the inputs. Producing a new frequency component other than what were in input (Is this assumption correct?) This is contrary to definition of linear systems I assume. So is this process linear, if not, how is it non-linear, I mean the whats the physics? I've wondered this question from time to time and I know I probably have some wrong assumption some where. I would appreciate if someone clarify things for me or point out my wrong supposition(s).
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1$\begingroup$ Eventhough a qualitative discussion is quite possible on the basis of a physical definition of the system you mention, formally it is necessary to define the mathematical representation of the system, in order to talk precisely about the linearity (or any other) property of it. $\endgroup$– Fat32Commented Nov 20, 2016 at 19:26
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$\begingroup$ I think, I have had a misassumption on blending of colors. The fact is, they do not blend when we see them. Actually they feel to be mixed because of our receptors in our cornea. So nothing non linear or linear happens, simply it is an perception and illusion. $\endgroup$– MimSaadCommented Jul 4, 2017 at 20:10
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Your mistake is that you are describing subtractive color mixing, not applicable in this scenario.
If you shed two lights onto a diffuse surface that does not absorb any light, and collect all the light diffusely reflected, the sum will be an additive mixture of the two. Incoherent (non-laser) light can be thought of as noise that has some electromagnetic spectral power distribution. From the signal processing point of view, long-time average power spectra of independent noise signals mix additively when they are summed
answered Nov 20, 2016 at 21:03
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$\begingroup$ Thanks for responding, From the signal processing point of view, long-time average power spectra of independent noise signals mix additively when they are summed, so you mean light blending (either subtractive or additive) is a random process? $\endgroup$– MimSaadCommented Nov 24, 2016 at 8:11
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$\begingroup$ @MimSaad Sorry I have no time to answer now, but here are some links to read: en.wikipedia.org/wiki/Electromagnetic_field en.wikipedia.org/wiki/Diffuse_reflection and also note that subtractive mixing is much harder to model so don't go into it if you can avoid it. If you really must understand subtractive color mixing there is the Kubelka-Munk theory. $\endgroup$ Commented Nov 24, 2016 at 10:48