An electric dipole of moment \[\vec{P}\] is placed in a uniform electric field \[\vec{E}\]. If the dipole is slightly rotated about an axis perpendicular to the plane containing \[\vec{E}\] and \[\vec{P}\] passing through the center of the dipole, the dipole executes simple harmonic motion. Consider I to be the moment of inertia of the dipole about the axis of rotation. What is the time period of such oscillation?

• A. \[\sqrt{\left( pE/I \right)}\]
• B.         \[2\pi \sqrt{\left( I/pE \right)}\]
• C. \[2\pi \sqrt{\left( I/2pE \right)}\]
• D.        None of these