Question

A caesium photocell , with a steady potential difference of `60 V` across , is alluminated by a bright point source of light `50 cm` away. When the same light is placed `1 m` away the photoelectrons emitted from the cell
A. Are one quarter as numerous
B. Are half as numerous
C. Each carry one quarter of their previous momentum
D. Each carry one quarter of their previous energy

Answer 1

Correct Answer - A
Number of photo electrons
`(N) prop Intensity prop (1)/(d^(2)) rArr (N_(1))/(N_(2)) = ((d_(2))/(d_(1)))^(2)`
`rArr (N_(1))/(N_(2)) = ((100)/(50))^(2) = (4)/(1) rArr N_(2) = (N_(1))/(4)`.