# Two Stefan Boltzmann Laws

by PatF
Tags: boltzmann, laws, stefan
 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?
 P: 1,958 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
 P: 17 Thanks much! I just checked and I think you are right.

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