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Two Stefan Boltzmann Laws

by PatF
Tags: boltzmann, laws, stefan
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PatF
#1
Apr24-12, 07:10 PM
P: 17
In Reif's book Fundamentals of Statistical and Thermal Physics, he labels two formulas as the Stefan-Boltzmann Law. They are both involve T^4 but the constant is different. In one, on page 376, the law is given as (pi2/15)*(kT)4/(c*hbar)3.

The other, on page 388, is (pi2/60)*(kT)4/(c2*hbar3).

The second formula is c/4 times the first.

I have looked carefully through the text and I can't see why there should be a difference. What have I overlooked?
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phyzguy
#2
Apr25-12, 07:08 AM
P: 2,179
I don't have the book, but probably they are not the same - one is referring to the intensity of emitted radiation, and the other is referring to the energy density of radiation. The two differ by a factor of c/4. Try this:

http://hyperphysics.phy-astr.gsu.edu...m/raddens.html
PatF
#3
Apr25-12, 08:39 AM
P: 17
Thanks much! I just checked and I think you are right.


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