Why does red light plus green light make yellow if photons don't interact?

[cragar]

when i mix red light and green light i get yellow light, but QED says that photons do not interact so why am i seeing yellow light, , I know they obey superposition , what does it mean for two photons two superimpose physically . how is the localized energy of the photons interacting .

 

[Stonebridge]

What you see here is nothing to do with photons interacting.
It is a consequence of the way our eyes are sensitive to light.
The eye has 3 types colour receptor, each sensitive to a different overlapping range of wavelengths of visible light. All the various phenomena relating to the mixing and combining of colours depend on this.
Wiki has a good article on colour vision.
http://en.wikipedia.org/wiki/Color_vision#Physiology_of_color_perception

 

[JDługosz]

when i mix red light and green light i get yellow light,

See http://www.handprint.com/HP/WCL/wcolor.html" for all the gory details.

--John