A photoelectric cell is illuminated by a point source of light `1 m` away . When the source is shifted to `2 m` then

Options

A. carry `1//4^(th)` of their previous energy
B. carry `1//4^(th)` of their previous momenta
C. are `1//2` as numberous
D. are `1//4` as numerous

Answer

D

Explanation

For a point source, `I prop 1//r^(2) prop` number of electrons
`(n_(2))/(n_(1)) =((r_(1))/(r_(2))) =((1)/(2))^(2) =(1)/(4)`