Re: Human perception of infrared

[Duane Westwood Degn <ddegn@xxxxxxxxxxxx>]

Aaron Ferrucci wrote:

>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=20
>.00075 mm. =20
>
>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=20
>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

It might be helpful to change the experiment from red light to radio =
waves (a very low frequency light or "electromagnetic radiation") and =
the receptor from the eye to a radio receiver.  I remember figuring the =
wavelength of my radio-controlled airplane transmitter (72.29MHz) to be =
approximately 4 meters (a far cry from 750nm).  I don't have to be more =
than 4 meters away from the receiver for the system to work.  Light =
waves are different from other waves we normally experience.  Unlike =
other waves light waves do not require a medium to travel which makes =
for all sorts of interesting things such as the special theory of =
relativity.  Light is very interesting stuff I minored in physics but =
still feel like I know just the tip of the ice burg about light.

Duane W. Degn
*
****
*******
******************************************************
*  To remove yourself from this list, send:          *
*         UNSUBSCRIBE INFRARED                       *
*       to                                           *
*         MAJORDOMO@xxxxx                            *
*----------------------------------------------------*
*   For the IR-FAQ, IR-Gallery and heaps of links:   *
*  http://www.a1.nl/phomepag/markerink/mainpage.htm  *
******************************************************

------------------------------

End of Infrared-Digest V0 #150
******************************