Polarised wave

A polarised wave is a transverse wave where the oscillations (vibrations) occur in a single plane or direction.

This becomes easier to think about if you use the example of a light wave:

• normally, a light will have oscillations occurring in multiple planes (in lots of different directions).
• but when the light is polarised, the oscillations only travel in one plane (in one specific direction).

So, some definitions:

• Polarised wave: a transverse wave where the oscillations occur in a single plane or direction.
• Unpolarised wave: a transverse wave where the oscillations occur in multiple planes or directions.

Longitudinal waves and polarisation

Longitudinal waves cannot be polarised. This is because the oscillations in a longitudinal wave occur in the same direction as the wave is travelling, so there is no other plane or direction for the oscillations to occur in.

This is actually a useful property, because it means we can tell apart transverse and longitudinal waves by checking whether they can be polarised or not.