What is the depth at which the value of acceleration due to gravity becomes $1\over n$ times the value that at the surface of earth? (radius of earth = R)

(1) $R\over n$

(2) $R\over n^2$

(3) $R(n-1)\over n$

(4) $Rn\over (n-1)$

(1) $R\over n$

(2) $R\over n^2$

(3) $R(n-1)\over n$

(4) $Rn\over (n-1)$