Answer
R = $ 5.4\times 10^{-4} $ m
Work Step by Step
We know that
$ V = \frac{q}{4\pi\epsilon R} $
This simplifies to:
$ R = \frac{q}{4\pi\epsilon V} $
We substitute the known values to obtain:
$R=\frac{3\times10^{-11}}{4\pi(8.85\times10^{-12})(500)}\\\\
R = 5.4\times 10^{-4} m$
