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From: ins_apmj@jhunix.UUCP (Patrick M Juola)
Newsgroups: net.sci
Subject: Re: Questions on PHOTONS
Message-ID: <1126@jhunix.UUCP>
Date: Fri, 8-Nov-85 13:09:33 EST
Article-I.D.: jhunix.1126
Posted: Fri Nov  8 13:09:33 1985
Date-Received: Sun, 10-Nov-85 16:54:32 EST
References: <1092@mtuxo.UUCP>
Reply-To: ins_apmj@jhunix.ARPA (Patrick M Juola)
Organization: Johns Hopkins Univ. Computing Ctr.
Lines: 52
Summary: answers to questions

In article <1092@mtuxo.UUCP> 45223wc@mtuxo.UUCP (w.cambre) writes:
>What's a photon?
A "piece" of light, or more specifically one quantum unit of a given frequency.

>What happens when two photons hit each other?
They just go through each other, like waves in water.

>Do photons lose energy when they bounce off things?
If they are absorbed and readmitted, yes.  If the thing is moving away (making
a Doppler shift), yes.  Otherwise, no.

>Do photons lose more energy when they bounce off black things
>than when they bounce off white things?
No.

>How about mirrors?
What about them? All a mirror does is reflect coherently, rather than scatteringthe light about.

>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
                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
You can't GET a mirror like that; it violates conservation of energy.

>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?
>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?
What would happen would be that the mirror warms up to white-hot, so it
shines light away as fast as you put it in.

>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, it does.  Well, actually, the energy of a photon is related to 
the wavelength of the light it represents.  This is related to the
wave-particle duality of light; light is both a stream of discrete
photons and a bunch of electromagnetic waves simultaneously; the waves 
have a wavelength, the photon merely has energy which is equal to the 
speed of light times Plank's constant over the wavelength.

>
>Does anybody really know?
>
No, all this is just a theory, but it's a fairly strong one.  Does anyone
really know that all mammals have hair?  Nothing in science is ever definite.

> - Bill Cambre   {ihnp4!}mtuxo!45223wc

							Pat Juola
							Johns Hopkins Univ.
							Dept of Maths