Why sound cannot be polarised
● VERBATIM — examined word-for-wordSound is longitudinal: oscillations are parallel to the direction of energy transfer, so there are no oscillations in the plane normal to the propagation direction to restrict. Restricting them would stop the wave itself. Three-line template — learn the chain.
What this actually means
Polarisation works by killing off oscillation directions in the plane perpendicular to travel. Sound has nothing in that plane: all of its oscillation points along the travel direction.
So a slit at any angle changes nothing. And if you somehow blocked the parallel oscillation, you would not have polarised the wave, you would have stopped it existing.
Write it as a three-step chain: sound is longitudinal → oscillations are parallel to the energy transfer → there are no oscillations in the normal plane to restrict. Each arrow is roughly a mark.
Prove it — watch it be true
- Switch to the longitudinal mode
- Rotate the slit through a full turn — the transmitted wave never changes
- That absence IS the answer: nothing oscillates in the perpendicular plane for the slit to block