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:
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Answer
(2) [figure]
Solution
Photocurrent is directly proportional to the intensity (and hence the power) of the incident light. Since power decreases linearly with time t, the photocurrent I also decreases linearly with time t.
The stopping potential depends only on the frequency of incident radiation and the work function of the metal: e|V0| = h - . It is independent of the power or intensity of light.
Therefore, the magnitude of the stopping potential |V| remains constant with time.
This behavior is correctly depicted in option (2).
Answer: (2)