A thin copper ring of radius ‘a’ is charged with q units of electricity. An electron is placed at the centre of the copper ring. If the electron is displaced a little, it will have frequency.

• A

  $\frac{1}{2\mathrm{\pi }}\sqrt{\frac{\mathrm{eq}}{4{\mathrm{\pi \epsilon }}_0{\mathrm{ma}}^3}}$

• B

  $\frac{1}{2\mathrm{\pi }}\sqrt{\frac{\mathrm{q}}{4{\mathrm{\pi \epsilon }}_0 {\mathrm{ema}}^3}}$

• C

  $\sqrt{\frac{\mathrm{eq}}{4{\mathrm{\pi \epsilon }}_0\mathrm{ma}}}$

• D

  $\sqrt{\frac{\mathrm{q}}{4{\mathrm{\pi \epsilon }}_0 {\mathrm{ema}}^3}}$