Q: The metallic bob of a simple pendulum has the relative density ρ. The time period of this pendulum is T. If the metallic bob is immersed in water, then the new time period is
(a) $ \displaystyle T( \frac{\rho -1}{\rho}) $
(b) $ \displaystyle T (\frac{\rho }{\rho-1}) $
(c) $ \displaystyle T \sqrt{\frac{\rho -1}{\rho}} $
(d) $\displaystyle T \sqrt{\frac{\rho }{\rho -1}} $
Ans: (d)