(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The equation of state PV= U/3 applies to a photon gas at pressure P, volume V and internal energy U. By using the 'energy equation', show that the internal energy of a phont gas is proportional to the fourth power of temperature (i.e U [itex]\propto[/itex]T[itex]^{4}[/itex]). You can assume that U/V is only a function of temperature.

2. Relevant equations

Energy equation: (dU/dvV)[itex]_{T}[/itex] = T (dP/dT)[itex]_{V}[/itex] - P

3. The attempt at a solution

U = 3PV

(dU/dV)[itex]_{T}[/itex] = 3P as (dP/dV)[itex]_{T}[/itex] = 0 as it is only a function of T

From here.. I'm not sure what to do. Help?

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# Homework Help: Thermodynmaics- Energy equation

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