Dan Crowe made a good point. The original question about rainbows by
Julie Quah may be interpreted two ways. I answered it through my own
"colored lenses," so to speak. (Pun intended!) For the last several
summers I have been the physics consultant to a middle school science
curriculum project, and there always seems to be questions about 'how
we see. color." I would rather have students begin to get an
understanding about image formation through geometric optics, but
either there are too many biologists on our state curriculum
committees or this is a burning issue. I am guessing it is coded into
Virginia's Standards of Learning (and whatever form many other states
have, also). So, Julie, did any of these answers help?
I do agree with Michael Edmiston that our eyes are somewhat like a
CRT in having three color receptors. But with my perspective on the
question having to do with spatial separation of color on the retina,
I'll try to clarify my response more fully. (I should have done this
originally.) In the CRT, the beam of electrons from the electron gun
must arrive fairly precisely at the spatial location of one of the
three color phosphors for that color to be transmitted. While in the
eye, it is the wavelength of the light that determines which receptor
is turned on and how much; light coming through the lens of our eye
impinges on all three receptors at a"pixel" location in our eye. I
was thinking that the CRT with its spatially separate phosphors may
have been the model Julie was initially relating and thus I said our
eye is not a CRT.