Within a spherical charge distribution of charge density $ρ(r), N $ equipotential surfaces of potential $V_0, V0+∆V, V_0+2∆V, .......... V_0+N∆V (∆V>0)$, are drawn and have increasing radii$ r_0, r_1, r_2,..........r_N$, respectively. If the difference in the radii of the surfaces is constant for all values of $V_0$ and $∆V$ then :

Question

$\begin{array}{1 1}(1) ρ (r) \propto r \\ (2) ρ (r) = constant \\ (3) \rho (r) \propto \frac{1}{r} \\ (4) \rho (r) \propto \frac{1}{r^2} \end{array} $