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)