- #1
4everphysics
- 19
- 0
Dear all,
I am using stress-energy tensor to derive equation of state of photon gas (assuming it as a perfect fluid).
I completed all the steps except one:
average value of [cos(θ)]^2 over unit sphere = 1/3.
I have no idea how this is so. (θ is polar angle).
I tried integrating over 0<θ<∏ and 0<φ<2∏, and then divided by the surface area of the sphere, but no luck with that either...
Please help!
I am using stress-energy tensor to derive equation of state of photon gas (assuming it as a perfect fluid).
I completed all the steps except one:
average value of [cos(θ)]^2 over unit sphere = 1/3.
I have no idea how this is so. (θ is polar angle).
I tried integrating over 0<θ<∏ and 0<φ<2∏, and then divided by the surface area of the sphere, but no luck with that either...
Please help!