Not actually a homework question, this is a question from a past exam paper (second year EM and optics): 1. The problem statement, all variables and given/known data Use a Gaussian surface and Amperian loop to derive the electrostatic boundary conditions for a polarization field P at an interface between media 1 and 2 with relative permittivities εr1 and εr2. 2. Relevant equations D = ε0E + P, [itex]\nabla[/itex].P = -ρb where D is the displacement field, E the electric field and ρb the bound volume charge density. 3. The attempt at a solution Lack of a solution is the reason for posting? Thanks in advance.