A rod of uniform diameter is suspended from one of its ends in vertical plane. The mass of the rod is ' \(m\) ' and length ' \(l\) ', the natural frequency of this rod in \(\mathrm{Hz}\) for small amplitude is

(a) \(\frac{1}{2 \pi} \sqrt{\frac{g}{l}}\)

(b) \(\frac{1}{2 \pi} \sqrt{\frac{g}{3 l}}\)

(c) \(\frac{1}{2 \pi} \sqrt{\frac{2 g}{3 l}}\)

(d) \(\frac{1}{2 \pi} \sqrt{\frac{3 g}{3 l}}\).