A thin, non-conducting spherical shell of radius R carries a total charge Q that is distributed uniformly over its surface.
a. (i) Prove that the electric field at any point located inside the shell (r<R) is zero.
b. (ii) Derive an expression for the magnitude of the electric field at a point P situated at a distance r from the centre when r>R.
c. (iii) Draw a qualitative graph to show the variation of the magnitude of the electric field with the radial distance r for 0≤r≤2R, marking all important values on the axes.