Question

Assertion (A): Photoelectric effect is a spontaneous phenomenon.

Reason (R): According to the wave picture of radiation, an electron would take hours/days to absorb sufficient energy to overcome the work function and come out from a metal surface.

Options

• Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

• Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

• Assertion (A) is true, but Reason (R) is false.

• Both Assertion (A) and Reason (R) are false.

Answer 1

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

Explanation:

The photoelectric effect is a spontaneous/instantaneous phenomenon, meaning there is no measurable delay between light hitting the metal and electron emission.

According to the classical wave picture of radiation, energy is spread over a wavefront, meaning electrons would need to absorb energy for a significant period (hours or days) to overcome the work function.

The contradiction between the instantaneous reality (A) and the delayed prediction of wave theory (R) proves that light behaves as particles (photons) that transfer energy immediately, rather than as continuous waves.