A caesium photocell, with a steady potential difference of `60 V` across, is illuminated 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

Options

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

A

Explanation

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)`.