Electromagnetism –revising with past exam papers

[The black vegetable]

Homework Statement

trying to do question C

Homework Equations

I know my answer to C cannot be right because it's worth six marks, any help or tips would be greatly appreciated. :)

The Attempt at a Solution

 

[TSny]

Check to see if you have the correct relation between D and E.

 

[The black vegetable]

thanks TSny you're right I have got that the wrong way round, I am more perplexed by question c though, how to find the free surface density, if I had the correct value for the displacement field of the dielectric would my answer for c be right? I'm assuming it wouldn't as it's awarding 6 marks, so must be more complex.

 

[TSny]

I think your answer for (c) would be correct once you use the correct expression for D in terms of E. Maybe they feel that (c) requires more conceptual thought in using Gauss's law for D.

 

[The black vegetable]

ok great thanks TSny