There are two large parallel metallic plates `S_(1)` and `S_(2)` carrying surface charge densities `sigma_(1)` and `sigma_(2)` respectively `(sigma_(1) gt sigma_(2))` placed at a distance d apart in vacuum. Find the work done by the electric field in moving a point charge q at distance `a(a lt d)` from `S_(1)` towards `S_(2)` along a line making an angle `pi//4` with the normal to the plates.

Explanation

Work done ` = fd cos theta = q Ed = cos theta (q(sigma _1 - sigma _2))/(epsi _0) (a)/(sqrt2) `