1. The problem statement, all variables and given/known data The work done in bringing a charge +q from infinity in free space to a postion at a distance D in front of a semi-infinite grounded metal surface? 3. The attempt at a solution Actually i know the method to solve it, but didn't understand its logic. F=[-1/(4pi*e0)](q*-q)/(2d*d) When we integrate this F as integral of F.dr between the limits x= d and x= infinity we get the result. my question is what is this semi infinte grounded metal? how does this (2d*d) appear in the denominator? des this q and -q appears because of induction charging ?