Two loops $P$and $Q$are made from a uniform wire. The radii of $P$and $Q$ are ${{r}_{1}}$ and ${{r}_{2}}$respectively, and their moments of inertia are ${{I}_{1}}$ and ${{I}_{2}}$respectively. If ${{{I}_{2}}}/{{{I}_{1}}=4}\;$ then $\frac{{{r}_{2}}}{{{r}_{1}}}$ equals