If R is the radius of the earth, the height at which g will decrease by `0.1%` of its value at the surface of the earth is

Options

A. R/6400
B. R/2000
C. R/1000
D. R/500

Answer

b

Explanation

`g_(h)=g(1-(2h)/(R))=100(1-(2h)/(R))`
`(2h)/(R)=1-(999)/(1000)=(1)/(1000)`
`h=(R)/(2000).`