Consider the arrangement of charges described in Exercise 23.23.
(a) Derive an expression for the potential V at points on the y-axis as a function of the coordinate y. Take V to be zero at an infinite distance from the charges.
(b) Graph V at points on the y-axis as a function of y over the range from y = -4a to Y = +4a.
(c) Show that for y » a, the potential at a point on the positive y-axis is given by V = - (1/4πє0)2qa/y2.
(d) What are the answers to parts (a) and (c) if the two charges are interchanged so that +q is at y= + a and -q is at y= -a?