Which phenomena proves the particle nature of photon?

The correct answer is Option (4) → Photo electric effect

A phenomenon shows the particle nature of light when light must be treated as packets of energy \( h\nu \) (photons) that are absorbed one at a time. Phenomena that need superposition of waves show its wave nature instead.

In the photoelectric effect the maximum kinetic energy depends on frequency, not intensity, and emission is instantaneous. These facts are explained only if one photon gives all its energy \( h\nu \) to one electron.

Note: A similar question was also asked in CUET (UG) 2023 on 26-05-2023 (Slot 1) and on 23-05-2023 (Slot 3).

NCERT (2026-27):
Wave Nature of Matter – “The dual (wave-particle) nature of light (electromagnetic radiation, in general) comes out clearly from what we have learnt in this and the preceding chapters. The wave nature of light shows up in the phenomena of interference, diffraction and polarisation. On the other hand, in the photoelectric effect and Compton effect which involve energy and momentum transfer, radiation behaves as if it is made up of a bunch of particles — the photons.”