From: Stirling Westrup (sti@cam.org)
Date: Sun Mar 26 2000 - 06:58:24 MST
>From: EvMick@aol.com
>I guess I'm "not getting it"..
>
>One molecule of gas....it absorbs energy.......then what?
Remember, energy comes in chunks. So, one molecule of gas is slammed into
by a photon moving at lightspeed, and absorbs it. This gives the molecule
a kick in the direction that the photon was moving. How much the molecule
speeds up, and exactly how it moves depends strongly on the energy
(frequency) of the photon, the shape of the molecule and what part
absorbed the photon. Now, not only will the molecule be moving faster, but
it will be in an energized (excited) state, and will at some point in the
near future fire off a photon in some (usually random) direction, so that
it can return to its normal state. Of course, when it fires off a photon,
it recoils and slows down, changing direction as it does.
Now if this is happening in a gas, where molecules are common, the photon
that was just fired off isn't going to get very far before it hits some
other molecule and is absorbed. You can easily imagine that even in a
really cold gas that has only one photon to bat back and forth, the
molecules are going to keep absorbing and firing off the photon and moving
further apart from each other, until they are finally far enough apart
that the photon doesn't hit anything, and escapes.
This is the physics behind Boyle's law, that relates presure (P),
temperature (T) and volume (V) in a gas. PV=kT, where k is a constant that
depends on the gas.
--
Stirling Westrup | Use of the Internet by this poster
sti@cam.org | is not to be construed as a tacit
| endorsement of Western Technological
| Civilization or its appurtenances.
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