Practice portal › Wave Optics › Polarisation
Asked in GSEB Board August 2020 · Malus's law and polaroids
Idea: a transverse wave vibrates across its direction of travel, so it can be treated differently according to how that direction is oriented; a longitudinal wave offers no such handle.
Reflection, refraction, interference and diffraction are all shown by sound waves, which are longitudinal, so none of them can decide whether light is transverse.
Polarisation is different: a polaroid passes only the vibrations along one direction in the plane across the ray.
Light really does get cut down, and then blocked altogether, as a second polaroid is turned, which is only possible if the vibrations are perpendicular to the direction of travel.
So it is polarisation that shows light to be transverse.
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