Expressing entropy of black body radiation

[desertgirl]

Homework Statement

By applying the first law to a quasi static process, show that the entropy can be expressed as
S = (16σ/3c) VT³

Homework Equations

U = 4(σ/c) VT⁴
PV = 1/3 U[/B]

The Attempt at a Solution

I know I should be using
dS = dQ/T but it's unclear to me how to use this unless I took the integral for arbitrary volumes, I couldn't find any examples in my text or online to try and get it myself [/B]

 

[TSny]

Hello, and welcome to PF!
Show how you are attempting to apply the first law.