Re: retro-reflection from cats' eyes

[jmclean@chem.ucsd.edu (James Mclean)]

Mark Sylvester says:
> Does anyone have a physical explanation for how the tapetum enhances vision
> in low light?
My book on cats describes the tapetum as reflective, made of 'glittering'
cells.  So I presume it enhances low-light vision by reflecting light back
through the receptors.  Light that doesn't get absorbed on the first time
through may be absorbed on the way back.

Why green?  From an evolution point of view, I'd hazzard a guess that green
light dominates the light in forest understories, all the other colors
having been absorbed by the plants.

The description of the tapetum cells as glittering has me wondering if they
achieve reflection through interference, which would explain why they have
a color at all.  That idea was inspired by an article in a recent American
Scientist about irridescent coloring in tropical plants -- a few plants
actually are colored not due to natural dyes, but because of interference
effects.  A very interesting article.

-- 
--James McLean
jmclean@chem.ucsd.edu
post doc
UCSD