Electric field direction and permittivity

1. Apr 24, 2013

zrek

The electric field direction can be measured by the force affected on a test charge.

Let's put a point-like charge not far from a material, that is polarized by it.
See the figure:

The test force on the test charge A points exactly to the charge.

I think that because the surface is full of polarized particles in one direction, the test charge next to the surface (C) will behave differently, the force on it will points more perpendicular to the surface.

And also the inner test charges (like B) will be under the effect of the neighbour particles, so the direction of the force will point a little towards the surface.

Is this effect possible? Can the permittivity affect to the direction of the force?

2. Apr 24, 2013

Staff: Mentor

There should be a slight deviation due to the material below it.
Yes it can.

3. Apr 24, 2013

zrek

Is it calculatable somehow? For example like the Snell's law?

4. Apr 24, 2013

Staff: Mentor

With the boundary conditions for electromagnetic fields - the parallel component of E and the perpendicular component of D are continuous, the field inside the material and outside are divergence-free, and D and E are proportional to each other* with some material constants.

For the surface, this should give something similar to Snell's law I think.

*there are materials where this is not true. It does not change the basic concept, however.

5. Apr 24, 2013

zrek

Am I understand it well that inside the material the force on the test charge points (in avarage) exactly to the main point-charge?

6. Apr 24, 2013

Staff: Mentor

No, the direction there will be changed by the material, too.

7. Apr 25, 2013