| Topic: |
Science > Physics |
| User: |
"mike3" |
| Date: |
09 Aug 2005 09:59:09 PM |
| Object: |
Black body radiation |
Hi.
Could you explain the mechanism of "black body" radiation emitted from
a hot object? How does a heated substance give off electromagnetic
radiation? Thanks for any answers.
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| User: "Zigoteau" |
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| Title: Re: Black body radiation |
10 Aug 2005 03:31:23 AM |
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Hi Mike,
Could you explain the mechanism of "black body" radiation emitted from
a hot object? How does a heated substance give off electromagnetic
radiation? Thanks for any answers.
Is this your homework?
Cheers,
Zigoteau.
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| User: "Uncle Al" |
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| Title: Re: Black body radiation |
10 Aug 2005 10:45:07 AM |
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mike3 wrote:
Hi.
Could you explain the mechanism of "black body" radiation emitted from
a hot object? How does a heated substance give off electromagnetic
radiation? Thanks for any answers.
Do you want the explanation from the point of view of the walls or the
free volume of cavity radiation? Both give the same answer (duals).
Crack a textbook.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
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| User: "mike3" |
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| Title: Re: Black body radiation |
10 Aug 2005 03:49:49 PM |
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Uncle Al wrote:
mike3 wrote:
Hi.
Could you explain the mechanism of "black body" radiation emitted from
a hot object? How does a heated substance give off electromagnetic
radiation? Thanks for any answers.
Do you want the explanation from the point of view of the walls or the
free volume of cavity radiation? Both give the same answer (duals).
Crack a textbook.
How is it emitted from heated solid, liquid, or gaseous matter? What is
going on with the atoms to emit the photons?
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
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| User: "Zigoteau" |
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| Title: Re: Black body radiation |
11 Aug 2005 03:39:22 AM |
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Hi Mike,
Could you explain the mechanism of "black body" radiation emitted from
a hot object? How does a heated substance give off electromagnetic
radiation? Thanks for any answers.
How is it emitted from heated solid, liquid, or gaseous matter? What is
going on with the atoms to emit the photons?
You haven't answered me, but I will give you the benefit of the doubt
that this is not a homework question.
Matter is made up of charged particles, which interact with each other
via Maxwell's electromagnetic field and move according to the laws of
quantum mechanics. When a body is heated up, it emits more radiation
because the charged particles in it have more energy.
The particles in normal matter that interact most strongly with
radiation are the electrons. This is a result of the fact that their
ratio of charge to mass, e/m, is three orders of magnitude higher than
that of any of the other component particles.
In classical mechanics, any accelerated charge emits electromagnetic
radiation. The electrons in an atom are accelerated by the strong
electric field of the nucleus. However in quantum mechanics, this only
sometimes leads to the radiation of power. Quantum mechanics describes
accurately what is actually observed. If you have more questions, you
need first to indicate your willingness to put in the effort to
understand QM.
You talk about black-body radiation. There is no such thing as a body
that is absolutely black, there are only approximations to blackness.
Bodies that are not completely black still give off electromagnetic
radiation when heated, just not as much. If you put a thin iron wire in
a flame, it will glow a bright red or yellow, while the flame is a much
less intense blue. The wire is cooler than the flame heating it, but
emits much more radiation because it is almost black, while the latter
is almost transparent.
People talk about "black body radiation" because they need to have some
sort of absolute yardstick of brightness to allow comparison between
groups. The closer to black you get, the more intense the radiation, up
to a certain limit. The best approximation to blackness is achieved
with a cavity.
Cheers,
Zigoteau.
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| User: "Sam Wormley" |
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| Title: Re: Black body radiation |
10 Aug 2005 07:42:02 AM |
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mike3 wrote:
Hi.
Could you explain the mechanism of "black body" radiation emitted from
a hot object? How does a heated substance give off electromagnetic
radiation? Thanks for any answers.
Mike, checkout: http://en.wikipedia.org/wiki/Blackbody
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