Photoelectric effect reveals the:

The correct answer is Option (2) → particle nature of radiation

In the photoelectric effect light ejects electrons from a metal only above a threshold frequency, with no time lag, and with a kinetic energy that depends on the frequency and not on the intensity. The wave picture cannot explain this; it needs light to arrive as discrete packets of energy \( h\nu \), the photons.

The effect therefore shows the particle nature of radiation. Interference, diffraction and polarisation are the phenomena that show its wave nature.

Note: A similar question was also asked in CUET (UG) 2023 on 31-05-2023 (Slot 2).

NCERT (2026-27):
Wave Nature of Matter – “… The wave nature of light shows up in the phenomena of interference, diffraction and polarisation. On the other hand, in 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.”