Entropy of blackbody radiation

In summary, The equation S = v\int_0^\infty\phi(\rho,\nu)d\nu, where \nu is the frequency of radiation, \rho(\nu) is radiation energy, and v is volume, is mentioned in Einstein's paper on the photoelectric effect. It is likely not an invention of Einstein, and can also be found in standard statistical mechanics textbooks such as Schwabl or Greiner's books. It is recommended to have a good understanding of statistical mechanics before attempting to understand this equation."
  • #1
learningphysics
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Can someone point out any information (derivation or where it comes from) about this equation:

[tex]S = v\int_0^\infty\phi(\rho,\nu)d\nu[/tex]

[tex]\nu[/tex] is frequency of radiation. [tex]\rho(\nu)[/tex] is radiation energy, v is volume.

I'm getting this from Einstein's photoelectric effect paper.

Thanks a lot!
 
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  • #2
Well,i haven't seen it in this actual form.Surely it wasn't an invention by Einstein.Did you check the formula for the entropy of BB radiation in a standard SM textbook,like Schwabl or Greiner...?Can u see the connection,then ?

Daniel.
 
  • #3
No. I haven't studied statistical mechanics (beyond very basic ideas of entropy), and don't have a text to compare.

I figured I'd probably need to have a good understanding of statistical mechanics before I could get through this paper. :yuck:

edit: Which SM text would you recommend?
 
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  • #4
Greiner's book in his series seemed accessible / readable enough and provided a wealth of worked out examples.

Daniel.
 
  • #5
http://www.iop.org/EJ/abstract/0143-0807/29/5/020"
 
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1. What is the concept of entropy in relation to blackbody radiation?

Entropy is a measure of the disorder or randomness in a system. In the context of blackbody radiation, it refers to the number of ways in which the energy of the radiation can be distributed among its different modes.

2. How does the entropy of blackbody radiation change with temperature?

The entropy of blackbody radiation increases with temperature. This is because as the temperature increases, the number of available energy states or modes also increases, leading to a higher degree of disorder or entropy.

3. What is the relationship between entropy and the Stefan-Boltzmann law?

The Stefan-Boltzmann law describes the total amount of energy emitted by a blackbody radiation per unit area. The law states that this energy is directly proportional to the fourth power of the temperature, which in turn is related to the entropy of the radiation.

4. What is the significance of the entropy of blackbody radiation?

The entropy of blackbody radiation is an important concept in thermodynamics and statistical mechanics. It helps in understanding the behavior of electromagnetic radiation and its interaction with matter. It also has implications in fields such as astrophysics and cosmology.

5. Can the entropy of blackbody radiation ever decrease?

No, the second law of thermodynamics states that the total entropy of a closed system can never decrease. This means that the entropy of blackbody radiation can only increase or remain constant, but it can never decrease.

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