Why are there two Stefan Boltzmann Laws in Reif's book?

[PatF]

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?

 

[phyzguy]

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/hbase/quantum/raddens.html

 

[PatF]

Thanks much! I just checked and I think you are right.