# Finding energy from a wave

1. Aug 30, 2009

1. The problem statement, all variables and given/known data
I need to find the energy transfered per unit time from a microwave oven, and the only information I have is:

Wavelength = .122m
Peak Magnetic Field of microwaves = 1.3*10^-5 T

2. Relevant equations
c=f*lambda
I = (c*B^2)/(permeability of free space) = EB / (permeability of free space)

3. The attempt at a solution
My problem is I need either "c" or "f" in c=f(lambda) OR the electric field..... I think? I'm not quite sure what to do.

2. Aug 30, 2009

### Redbelly98

Staff Emeritus
You can find I from the given B. Two more things to think about:

1. Using the peak B given will result in the peak of I. What will be the average of I?

2. How does I relate to power?

3. Aug 30, 2009

Ok, but I run into the same problems again. I have neither c nor E so Im stuck with 3 unknowns.

4. Aug 30, 2009

### Redbelly98

Staff Emeritus
But you do have c. Think about it ... what is c?

5. Aug 30, 2009