# Homework Help: Maxwell Stress Tensor

1. Aug 21, 2006

### golfingboy

URGENT!!

Hi, I have a couple of urgent problems which are listed below. I am not sure what to do in either of them! If someone could help me as soon as possible that would be great!

Cheers

Problems:

1. Consider a linearly polarised plane wave incident normally on a slab of material that absorbs it completely. Use the Maxwell stress tensor to show that the pressure exerted on th screen is = to the energy density of the incoming field. Check that this agrees with the simpler method of using the momentum density of the field

2. Two charges of q at a distance r repel each other according to Coulomb's Law. Choose a suitable surface sorrounding one of the charges and calculate F by integration of the Mawell stress tensor

Last edited: Aug 21, 2006
2. Aug 21, 2006

### Physics Monkey

Hi golfingboy,

If you're lost, it's always good to start at the start. What is the definition is the Maxwell stress tensor? You can begin by calculating what the stress tensor actually is in both situations. Now, how do you extract physically meaningful things from this object i.e. what does it do? Hint: think about integrals of the tensor over surfaces.