Consider a uniformly charged spherical shell. Two cones having same semi vertical angle, and their common apex at P, intercept the shell. The intercepts have area `DeltaS1` and `DeltaS2`. For a cone of very small angle, `DeltaS1` and `DeltaS2` will be very small and charge on them can be regarded as point charge for the purpose of writing electric field at point P. Prove that the charge on `DeltaS1` and `DeltaS2` produce equal and opposite field at P. Hence, argue that field at all points inside the uniformly charged spherical shell is zero.