In an experiment on the photoelectric effect, the frequency and inten…

The correct answer is Option (4) → It increases initially and then becomes constant.

With the frequency and intensity fixed, plate C emits a fixed number of photoelectrons per second. The positive potential of the collector only decides how many of them are collected.

Option (1) It increases. — Incorrect. The current rises only until every emitted electron reaches the collector. After that, a higher potential cannot collect more electrons than are emitted.

Option (2) It decreases. — Incorrect. The photocurrent falls when the collector is made negative (retarding) with respect to the emitter. A negative collector repels the electrons, but an accelerating potential attracts them.

Option (3) It remains constant. — Incorrect. At a low accelerating potential, not all the emitted electrons reach the collector. So the current first grows with the potential. It is constant only after saturation.

Option (4) It increases initially and then becomes constant. — Correct. As the positive potential rises, more of the emitted electrons are collected and the photocurrent increases. Once all the emitted electrons reach the collector, the current reaches its maximum, the saturation current, and stays constant.

NCERT (2026-27):
Effect of Potential on Photoelectric Current – “… We next vary the positive potential of plate A gradually and measure the resulting photocurrent each time. It is found that the photoelectric current increases with increase in positive (accelerating) potential. At some stage, for a certain positive potential of plate A, all the emitted electrons are collected by the plate A and the photoelectric current becomes maximum or saturates. If we increase the accelerating potential of plate A further, the photocurrent does not increase.”