Re: Human perception of infrared

[aaronf@xxxxxxxxxxxxxxxxx (Aaron Ferrucci)]

Bazpan@xxxxxxx wrote:

> ...
>
> The wavelength of red light is around 750nm. I believe this equates to
>  0.75mm. If you were to hold a red object such that it almost touched the
> surface of the eye (say half a millimetre away) you would presumably be able
> to perceive it as being red. Yet the light reflected from the object would
> have travelled less than a full wavelength before striking the eye. What am I
> missing here?
>

I can help a bit here: 750nm is actually .75 micrometers, or 
.00075 mm.  

I think the distance of interest is not the distance from
the red object to the eye, but from the red object to the
retina.

The question then becomes, what happens if you suspend a
red object 500nm from the retina (please, let's leave this
as a gedanken physics experiment, rather than try to figure
out how to actually _do_ this without destroying someone's
eyesight!).   Of course only a few retinal cells would be 
that close to the light source...

Well, that's as far as I can go - can anyone with a better
biophysics background shed some light?

- -Aaron

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