An electric dipole of dipole moment P is placed in a uniform electric field E in stable equilibrium position . It's moment of inertia about the centroidal axis is I . If it is displaced slightly from it mean position find the period of small oscillations .

Question

$(a)\;2\pi \sqrt{\large\frac{I}{PE}}\qquad(b)\;\pi \sqrt{\large\frac{I}{PE}}\qquad(c)\;\pi \sqrt{\large\frac{PE}{I}}\qquad(d)\;2\pi \sqrt{\large\frac{PE}{I}}$