Adiabatic exponent for photon gas and degenerate fermion gas

[Fys]

Homework Statement

1.Show that
$$PV^Y$$ is a constant for adiabatic,quassistatic expansion of a photongas and determine Y
2. Show the same for full degenerate gas of fermions at T=0

Homework Equations

The Attempt at a Solution

Plz help thx

 

[Hootenanny]

Do you have any ideas whatsoever? You must have something in your lecture notes...