Graphical variation of electric field due to a uniformly charged insulating solid sphere of radius R , &#160…

The electric field inside a solid insulated sphere is given by 

$E_{inside}=\frac{\rho r}{3{\epsilon }_0}$ for $r<R$ where $\rho$ is volume charge density.

Hence, the electric field varies linearly with the distance as

${\mathrm{E}}_{\mathrm{inside}}\propto r^1$

Now, the electric field for $r>R$ is given by 

$E_{outside}=\frac{Q}{4\pi {\epsilon }_0{r}^2}$

${\mathrm{E}}_{\mathrm{outside}}\propto \frac{1}{{\mathrm{r}}^2}$

Thus, the graph starts decreasing as a power law graph as shown in the figure for the region $r>R$.

Hence, this graph is the right option.