How does polarization show that light behaves as a transverse wave?

Polarization provides definitive evidence that light behaves as a transverse wave because it demonstrates that the oscillations associated with light occur at right angles to the direction of its propagation.123

In a longitudinal wave, such as sound, the disturbance moves parallel to the direction of the wave, meaning there is no "sidedness" or orientation to the vibration relative to the path of travel. Conversely, light exhibits polarization, a property where the electric field vector vibrates in a specific orientation perpendicular to the axis of propagation.241

If light were a longitudinal wave, it would be impossible to filter or restrict its vibrations to a single plane, as there would be no transverse component to isolate. The ability to polarize light—for instance, by passing it through filters or observing double refraction—confirms that light possesses the directional asymmetry characteristic of transverse motion. This realization, championed by Thomas Young and Augustin-Jean Fresnel, was essential to establishing the wave nature of light.251