Message-Id: <v01510103b37787930696@[205.134.240.103]>
Date: Sun, 30 May 1999 16:44:03 -0800
To: "Pinhole Listserv" <pinhole@exploratorium.edu>
From: bcomet@sirius.com (Burt C. Kessler)
Subject: Re: pinhole light, color, and lasers
>Quite possibly the last pinhole question from my ultra-bright crop of
>students, graduating this year:
>
>Do laser colors add in the same way that dispersed colors of light through
>a prism can be added to make white light?
>
>Why do light colors add in the ways that they do, anyway (i.e. green and
>red making yellow)? Is the phenomenon due to interference, or aspects of
>human perception, or something else?
>
The human retina has cones with three ranges of sensitivity: red-yellow,
green-yellow, and blue-violet. These are the three colors we actually see.
All other colors are combinations of these. Yellow light stimulates two
of these populations of cones and not the third. If we combine equal
amounts of red and green light, we stimulate the same pair of cones, so the
light looks yellow. We also percieve yellow when only blue is removed from
white light. The physiologic response of the cones is the same to all
three combinations of light frequencies.
White flourescent light, when viewed through a diffraction grating appears
to be only red, green, and blue-violet light. This looks white, just as a
monitor makes white with just three color phosphors. I would expect laser
light to add the same as any other light. Any combination of colors that
equally stimulates all three populations of cones should appear white.
Burt Kessler
The best thing about the future
is that it comes only one day at a time.
Abraham Lincoln