1. The problem statement, all variables and given/known data A point charge +q is initially at distance x from a conducting plane of infinite extent and held at zero potential. Find the work done in moving the charge to an infinite distance from the plane. Hence find the minimum energy an electron must have in order to escape from a metal surface (assume that it starts at a distance 0.1nm, which is about one atomic diameter, from it). Express your answer in electron-volts. [Answers: q^2/(16πε0x) ; 3.6eV] 2. Relevant equations U=q(V2-V1) Method of images 3. The attempt at a solution The plane can be replaced with a negative -q point charge at a distance 2x. Therefore the energy required to move the charge to infinity=q(0-(-q/(4πε02x)))=q^2/(8πε0x). Why did they put 16 in the answer??