A very long straight thread is oriented at right angles to an inifinite conducting plane, its end is seperated from the plane bya distance `l`. The thread carries a uniform charge of linear density `lambda`. Suppose the point O is the trace of the thread on the plane. find the surface density of the induced charge on the plane
(a) At the point O
(b) As a function of a distance r from the point O.

Answer

(a) `sigma=lambda/(2 pi l)`; (b) `sigma(r) =lambda/(2pi sqrt(l^(2)+r^(2)))`