# Wave intensity

1. Nov 21, 2009

### borvis

1. The problem statement, all variables and given/known data

I have two waves interferencing with the same wavelenght $$\lambda$$ and average intensity $$I_{o}$$. They also have a constant phasedifference of $$\varphi$$.

2. Relevant equations

The problem is that I dont know any equations or relations for the intensity of waves. I have a lousy compenium in this class.

3. The attempt at a solution

Im supposed to show that $$I_{tot}=4I_{o}cos(\frac{\varphi}{2})$$.

This is probably quite easy to show, but I'm really stuck. Some information about the intensity of classical waves would be really helpful. Thanks alot!