A photocell with a constannt potential differnce of V voolt across it, is illuminated by a point source from a distance of 25 cm. when the source is moved to a distance of 1 m, the electrons emitted by the photocell

Options

A. carry 1/4th their previous energy
B. are 1/16th as numerous as before
C. are 1/4th as numerous as before
D. cary 1/4th theirr previous momentum

Answer

B

Explanation

Photoelectric current `l` is directly proportional to intensity of light and intensity `prop(1)/(("distance")^(2)) implies l prop(1)/(r^(2))`
`l_(25) prop(1)/((25)^(2))` . .. (i)
`l_(100) prop(1)/((100)^(2))` [1m=100cm] . .. (ii)
`therefore (l_(25))/(l_(100))prop ((100)^(2))/((25)^(2))=16 implies l_(100)=(l_(25))/(16)`