A uniformly charged square whose side is 2s with surface charge density +s is lying in the xy plane. Find the electric field at point P lying on the axis collinear with the center of the square and a distance b from the center. Show that the electric field E at point P is

E = Q log {[b + s] x [s + (s^2 + (b - s)^2)^1/2]} (i^) /
16 {[b - s] x [s + (s^2 + (b + s)^2)^1/2]}

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