1. The problem statement, all variables and given/known data Exercise 1: Suppose a infinte plane z=0 divides the 3-dimensional space into two parts. The region below z=0 is filled with linear dielectric material of susceptibility [itex]\chi[/itex]. The bound charge density at z=0 is [itex]\sigma[/itex]. Find the electric field of the two regions. Exercise 2: The original problem in Griffith's book is to calculate the force on a point charge q situated a distance d above the the origion (x=0,y=0,z=d). The first step is to find the electric field [itex]E_z[/itex] just inside the dielectric at z=0, which is due in part to q and in part to the bound charge itself. And he states that the latter contribution is [tex]-\sigma/2\epsilon_0[/tex]. In my opinion, we should write two equations(from Guass's law in terms of E and D respectively): [tex]\epsilon_0 E_1+\epsilon_0(1+\chi)E_2=0[/tex] [tex]\epsilon_0(E_1+E_2)=\sigma[/tex] Then [itex]E_2[/itex] is my answer, which is quite different from the expression in Griffith's book [itex]-\sigma/2\epsilon_0[/itex]. I need a detailed solution to the electric field of this configuration.