Choose the phenomenon from the following, which shows that light is a transverse wave.

Polarisation

The correct answer is Option (4) → Polarisation

Polarisation is a property of transverse waves only, as it involves the oscillations being confined to a particular plane perpendicular to the direction of wave propagation.

Diffraction, interference, and reflection can occur for both transverse and longitudinal waves and do not confirm the transverse nature of light.