When a monochromatic point source of light is at a distance
of 0.2 m from a photoelectric cell, the cut off voltage and the saturation current
are respectively 0.6 V and 18.0 mA. If the same source is placed 0.6 m away
from the photoelectric cell, then
(a) the stopping potential will be 0.2 V
(b) the stopping potential will be 0.6 V
(c ) the saturation current will be 6.0 mA
(d) the saturation current will be 2.0 mA

Options

A. (i),(ii)
B. (ii),(iii)
C. (i),(iv)
D. (ii),(iv)

Answer

D

Explanation

Stopping potential is independent of intensity
`i prop I prop 1//d^(2)`
`(i_(2))/(i_(1)) =((r_(1))/(r_(2)))^(2) =((0.2)/(0.6))^(2) =(1)/(9)`
`i_(2) =(i_(1))/(9) =(18)/(9)=2 mA`