For a uniformly charged sphere of radius $R$ and charge density $\rho$, the ratio of magnitude of electric fields at distances $R / 2$ and $2 R$ from the centre,

i.e., $\frac{\mathrm{E}(r=\mathrm{R} / 2}{\mathrm{E}(r=2 \mathrm{R})}$ is $\ldots .$