Two light strings, each of length l, are fixed at points A and B on a fixed horizontal rod xy. A small bob is tied by both strings and in equilibrium, the strings are making angle 45° with the rod. If the bob is slightly displaced normal to the plane of the strings and released then period of the resulting small oscillation will be:

• A

  $2\mathrm{\pi }\sqrt{\frac{2\sqrt{2}\mathrm{l}}{\mathrm{g}}}$

• B

  $2\mathrm{\pi }\sqrt{\frac{\sqrt{2}\mathrm{l}}{\mathrm{g}}}$

• C

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{l}}{\mathrm{g}}}$

• D

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{l}}{\sqrt{2}\mathrm{g}}}$