1. SRH
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Jul 2012
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216

## questions about light and temperature

Have there been any experiments measuring the effects of changing temperatures on a photon's wavelength and frequency?
If so, were there any observed changes in the wavelength and frequency, and in which direction?
Thanks.

2. I'm not quite sure what you are asking. Temperature is effectively a measure of the (internal) energy of a material.

Are you asking what the effect of temperature is on the photons emitted by a hot body (e.g. black body radiation)? Or are you asking what the effect of the temperature of a material on transmitted light is? Or ... ?

3. SRH
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For some reason Strange, I can't PM you...
I'm trying to learn if it is possible if a colder vacuum in space (as starlight travels farther from the hot star that emitted it) could cause a redshift or a decrease in frequency in the emitted light.

Is this a dumb question because a vacuum does not have a temperature (i.e. only the matter in the vacuum has a temperature)? (That seems to be what you are saying)
If that is the case, then is there any observed effect on light's frequency and/or wavelength as it travels through a pool of water (a medium) with a very cold temperature versus a pool of water with a very hot temperature?

Also, could you please explain what black body radiation is in simple terms...I will check Wikipedia in the mean time.

Thanks.

4. A (perfect) vacuum does not have a temperature. But the interstellar/intergalactic medium (gas & dust) will have. That, generally, doesn't have much effect on light (apart from some scattering). I don't know how/if the temperature would affect that.

Temperature can have a very small effect on the refractive index of materials; mainly because it changes the density.

Black body radiation: you know how when you heat something up, it glows red then yellow then white as it gets hotter? Black body radiation is the spectrum that would be emitted by a perfect black surface at a given temperature (Wikipedia has a pretty good description). It is important to the history of quantum theory.

5. Order of Kilopi
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Originally Posted by Strange
A (perfect) vacuum does not have a temperature. But the interstellar/intergalactic medium (gas & dust) will have. That, generally, doesn't have much effect on light (apart from some scattering). I don't know how/if the temperature would affect that.

Temperature can have a very small effect on the refractive index of materials; mainly because it changes the density.

Black body radiation: you know how when you heat something up, it glows red then yellow then white as it gets hotter? Black body radiation is the spectrum that would be emitted by a perfect black surface at a given temperature (Wikipedia has a pretty good description). It is important to the history of quantum theory.
Strange. Good. There's a bit more here too. If you have your nice (gas-liquid-solid-plasma-free) vacuum...with it's attendent photon flux, and you shine your laser through it, you bring in to play Bose-Einstein statistics. Particles are classified according to their spin. Even integer spin particles are Bosons(photons go here). Half-integer spin particles are Fermions(electron, neutrons, protons go here). The first, bosons, obey Einstein-Bose statistics....after Albert &. S.N. Bose the Indian physicist. The second, Fermions, obey Fermi-Dirac statistics, after Enrico & P.A.M.Dirac. B-E statistics allow an infinite number of bosons to occupy the same volume of spacetime....soooo..... your laser beam will be unaffected by passing through another laser, ( sorry Luke Skywalker/Darth Vader)..or a sea of photons. But, F-D statistics will limit the number of Fermions that can occupy a given volume of spacetime (kind of like the Pauli exclusion principle in the hydrogen atom)...so they will interfere with other residing Fermions, and push on them. (This results in the Fermi degeneracy pressure that resists further contraction in a low mass neutron star...sub-Chandrasekhar) pete

SEE:http://en.wikipedia.org/wiki/Bose%E2...ein_statistics

SEE:http://en.wikipedia.org/wiki/Fermi%E...rac_statistics

SEE:http://universe-review.ca/R08-04-degeneracy.htm
Last edited by trinitree88; 2012-Aug-06 at 04:32 PM. Reason: links

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