Which one of the following can not be polarized?

The correct answer is Option (2) → Sound waves

Polarisation means restricting the vibrations of a wave to a single direction in the plane perpendicular to the direction in which the wave travels. This is possible only for a transverse wave, whose vibrations are perpendicular to its direction of travel.

Sound in air is a longitudinal wave: the air particles vibrate along the direction of travel itself. There is no sideways direction of vibration to select, so sound waves cannot be polarised.

Note: A similar question was also asked in CUET (UG) 2023 on 20-06-2023 (Slot 3).

NCERT (2026-27):
Points to Ponder – “… 4. Most interference and diffraction effects exist even for longitudinal waves like sound in air. But polarisation phenomena are special to transverse waves like light waves.”