|Authored by: bugstomper on Tuesday, March 19 2013 @ 06:31 AM EDT|
|That link is really funny - It is a forum thread that devolves into a flame war|
between two people who admit that they don't know the answer but spend their
time telling the other person how their conjectures that both admit are not
correct or complete are idiotic :)
The actual explanation, that I didn't see in the thread before I didn't have the
stomach to continue reading, is this:
We have three color receptors ("cones") which are called
"red", "green", and "blue" after the color to
which they are each most sensitive to. Each type of cone is sensitive to all
visible frequencies, in somewhat bell shaped curves.
When light of a pure red frequency strikes the eye, the red cone produces the
strongest signal, the green cone much less of one, the blue cone even less. The
brain interprets that mix of signals as the color red. Light of a pure yello
frequency will produce about equal signals in the red and green cones, much less
in the blue cone, for a mix of signals the brain interprets as the color
When you look at an rgb monitor that is producing red and green light in some
pixel, that produces the same signal pattern in the cones as pure yellow light
produces. The brain again interprets that signal pattern as the color yellow.
What if you had some blue light and a lesser amount of equal parts green and
red? That would stimulate the blue cones the most, and the red and green cones
less so in equal amounts. That would look like a light blue - equivalent to pure
blue plus some white.
Here is an interesting tweak in what the cones actually do: The red cone is most
sensitive to red frequency light, with sensitivity trailing off as the frequency
increases through the colors of the rainbow, orange, then yellow, then green,
then even less sensitive to blue. But going into the violet frequencies its
sensitivity increases slightly, not as sensitive to violet light as the blue
cone, but more than the green cone.
Now consider what happens with Rayleigh scattering: The violet scatters the
most, then blue, then green, then red hardly at all. When you look at the
scattered light in the sky, the blue cones are stimulated quite a bit by the
violet and the blue frequencies, green cones are stimulated by the smaller
amount of green frequencies, and the red cones are stimulated a little bit by
the large amount of scattered violet, and a little bit by the little bit of
scattered red. Because of the violet having some effect on the red cones, the
total stimulation of the green and red cones comes out to about the same. The
overall effect is blue cones getting much stimulation, then green and red cones
not so much but about the same as each other. That is the same recipe as I
described for light blue, and that is just how the brain perceives it.
[ Reply to This | Parent | # ]