This question was on our final, but I do not completely understand what the professor was trying to say. 1. The problem statement, all variables and given/known data "A charge Q is located at a distance d above an infinitely large grounded half-plane located in the x-y plane and at a distance d from another grounded half-plane in the x-z plane. Find the electric field at a point of coordinates x=y=0 and z=d." 2. Relevant equations E=Q/4pi(epsilon)r^2 Phi=Q/4pi(epsilon)r 3. The attempt at a solution I first thought to use image charges, but he never stated that the plane was conducting, and a nonconducting grounded plane does not necessarily have constant potential. So instead I simply found the electric field as if the plane was not there E=-Q/4pi(epsilon)d^2 (y hat) If I had assumed it was a conductor, wouldn't E just equal zero since the point is within the plane? The rest of the problems on the final took a very long and involved process to solve so either alternative to this question seemed out of place. How should I have gone about this problem?