Irodov Problem 3.56

Following the same argument as in Problem 3.54, we can treat the infinite conducting plane as a plane mirror. Hence, for each charge and equal and opposite image charge appears at the other end of the conducting plane as shown in the figure.

a)

There are three forces acting on the positive charge q as shown in the figure. The attactive forces F2 and F1 from the real and the image negative charges located at distances l each and the repulsive force F3 from the image charge located diagonally. The net force is given by,




b)


The electric field at the mid point of the two charges can be obtained by considering the electric field due to all the four charges - the two real charges and the two image charges. This is given by,