Question

Light of intensity 'I' and frequency 'v' is incident on a photosensitive surface and causes photoelectric emission. What will be the effect on anode current when (i) the intensity of light is gradually increased, (ii) the frequency of incident radiation is increased, and (iii) the anode potential is increased? In each case, all other factors remain the same.
Explain, giving justification in each case.

Answer 1

Given:-

Intensity of light=$I$

Frequency of light=$v$

solution:-

$1)$ As the intensity of light is gradually increased,the anode current also increases linearly. This is because the number of photo electrons emitted per second is directly proportional to intensity of incident light.

$2)$ If frequency of incident light is increased, the anode current remains constant as it is not affected, as long as the frequency is greater than the threshold frequency.

$3)$ In the beginning as the anode potential is increased, anode current also increases until it reaches a saturation. the anode current at this stage is called saturation current. after this if the anode potential increases, the anode current remains constant at saturation current.