How does polarization show that light is a transverse wave?

"Polarization" is when the orientation of a transverse wave is restricted to a particular plane. In other words, the very definition of "polarization" requires a transverse wave.

A plane is a two dimensional shape. The vibrations of a transverse wave are perpendicular to the direction of travel, so combining the two motions of the travel and vibrations leads to a 2D result. Transverse waves can therefore be confined to a plane – i.e they can be polarised.

The vibrations of longitudinal waves are parallel to the direction of travel. Combining these motions leads to a 1D result. Longitudinal waves cannot therefore be confined to a plane – i.e they cannot be polarised.

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