# Poynting's vector problem

1. Nov 21, 2008

### Jack_O

Problem:

Attempt:

I think I've done the first bit correctly (but I'm not certain). As for the second half of the question i'm at a loss. I have looked up poyntings vector and found S=ExH where H is the auxiliary magnetic field (i'm not sure what this means) and S=(1/u(0)) (ExB), but i'm not sure what to do with it.

Any help appreciated.

2. Nov 21, 2008

### naresh

In free space, the auxiliary field H is just $$B/\mu_0$$