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 :
B.
The power of the incident light is P = n h , where n is the number of photons incident per unit time and is the frequency. As the power decreases linearly with time, the number of incident photons n also decreases linearly, assuming the frequency remains constant. The photocurrent I is directly proportional to the number of incident photons per unit time (I n). Thus, the photocurrent I decreases linearly with time. The stopping potential V is given by Einstein's photoelectric equation e|V| = h - , where is the work function of the metal. Since the frequency and the work function are constant, the stopping potential |V| remains constant over time, independent of the light's power. Therefore, the graph of I versus t is a straight line with a negative slope, and the graph of |V| versus t is a horizontal line. Answer :
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