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From: peter@graffiti.UUCP (Peter da Silva)
Newsgroups: net.sci
Subject: Re: Questions on PHOTONS
Message-ID: <421@graffiti.UUCP>
Date: Sat, 9-Nov-85 10:29:39 EST
Article-I.D.: graffiti.421
Posted: Sat Nov  9 10:29:39 1985
Date-Received: Mon, 11-Nov-85 07:32:56 EST
References: <1092@mtuxo.UUCP>
Organization: The Power Elite, Houston, TX
Lines: 62

> What's a photon?

A packet of waves is as good a description as any.

> What happens when two photons hit each other?

They pass through each other. If the energy is high enough there may be
particle-pair creation at this point, but that's unlikely with the photon-
energies you're likely to meet.

> Do photons lose energy when they bounce off things?

No, though some observers may see a net loss or gain when the photon bounces
off a moving object, or one with a relatively low mass.

> Do photons lose more energy when they bounce off black things
> than when they bounce off white things?

No. It's just that more photons are absorbed by and fewer photons are reflected
from black objects.

> How about mirrors?

See above.

> If I have a hollow sphere with a mirror coating on the inside
> and a light source in it, and say the light cannot get out of the
> inside of the sphere, if I leave the light source on for a while,
> will the sphere fill up with photons?  Will it get full?

Only with perfect mirrors. Since you can't build a perfect mirror outside
a science fiction story the point is moot, but even if you could, eventually
it'd stop filling up:

The energy density on the sphere will increase. Some photons will escape due
to quantum effects, and eventually this tunneling will reach the point where
the same amount of energy escapes as is provided by the light. I guess you
could call this "full".

> Will it get brighter and brighter in there?  If I keep the light on
> in there for  30 years then suddenly break open the sphere, will
> I be blinded by all the light that explodes out of it?

Probably. I think it likely the sphere would explode unless you used Larry
Niven's "stasis feilds" or E.E. Smith's "Zone of Force".

> What's the difference between photons in a red light and photons in a
> blue light.  I thought red and blue light are energy in a certain
> wavelength.  Does a photon have a wavelength?

Yes. See answer to first question. As an excersize calculate the wavelength of
the monkey in the monkey-weight experiment. Calculate the probability of the
monkey turning into a potted plant and a very surprised sperm whale.

> Does anybody really know?

Yes, I think.
-- 
Name: Peter da Silva
Graphic: `-_-'
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