Q 12-11-002NEETNEET 2026Top questionEasy
A beam of light falls on a metal surface such that photo-electrons are generated. If power of the light source starts to decrease linearly with time $t$, then variation of the photocurrent $I$ and magnitude of the stopping potential $|V|$ with time is best represented by :
Answer: (A) see figure
The frequency of the light does not change, only its power (intensity).
Photocurrent is proportional to the number of photons arriving per second, which is proportional to the power. So $I$ decreases linearly with time.
The stopping potential depends only on the frequency: $e|V| = h\nu - \phi$. So $|V|$ stays constant.
The graph with $I$ decreasing linearly and $|V|$ constant is option (1).
Solution by Sreeraj P, M.Sc Physics