Question

A point source of light is used in an experiment of photoelectric effects. If the distance between the source and the photo-electric surface is doubled, which of the following may result ?

• A. Stopping potential will be halved
• B. photo-electric current will decrease
• C. Maximum kinetic energy if photo-electrons will decrease
• D. Stopping potential will increase slightly

Answer 1

Answer: (C)

Intensity $I\propto \frac{1}{d^2}$
and photo-electric current $\propto$ intensity
$\therefore$ Current will decrease