Question

A source of light, of frequency greater than the threshold frequency, is placed at a distance ‘d’ from the cathode of a photocell. The stopping potential is found to be V. If the distance of the light source is reduced to d/n (where n>1), explain the changes that are likely to be observed in the (i) photoelectric current and (ii) stopping potential.

Answer 1

AS  we know that  

I α 1/ r²

Therefore On reducing the distance r , intensity increases.

Photo electric current increases with the increase in intensity.

Stopping potential is independent of intensity and therefore remains unchanged.