What effect occurs on the frequency of a pendulum if it is taken from the earth surface to deep into a mine

Options

A. First increases and then decreases
B. Increases
C. Decreases
D. First decreases and then increases

Answer

C

Explanation

When it is taken to a depth d below the surface of the earth, g decreases `g'=g(1-(d)/(R ))`, where R is the radius of the earth and for a simple pendulum,
`n=(1)/(T)=(1)/(2p sqrt((l)/(g))) therefore n prop sqrt(g)`
`therefore` The frequency will also decrease.