# Homework Help: Blackbody Radiation Test Question

1. Oct 30, 2012

### cstang52

1. The problem statement, all variables and given/known data
The blackbody radiation equations of state are E/V=aT^(4) and P=(1/3)(E/V). From the fundamental state derive a quantity involving only P and V that remains constant when this radiation undergoes a reversible adiabatic transformation.

2. Relevant equations
Maybe dE=TdS-PdV being the fundamental state?

3. The attempt at a solution

2. Oct 30, 2012

### Oxvillian

I suggest starting with
$$dE = -p \; dV$$
since for an adiabatic process dS = 0. Then try to eliminate dE in favor of dp and dV.