🕶️ Polarization (Malus's Law)

📖 The Physics

Light is a transverse wave, so its vibrations can be lined up in a single direction — that lining-up is polarization. The first filter (the polarizer) lets through only the vertical vibrations.

A second filter (the analyser) then passes only the part of that light lying along its own axis, so the brightness follows Malus's law.

Rotate the analyser: at 0° all the light gets through, at 90° it goes dark (crossed polarizers), and at 45° exactly half passes. Only a transverse wave can do this — which is proof that light istransverse. It is used in sunglasses, LCD screens and photography.