Polarization of Light
Rotate polarizing filters and watch Malus's Law — I = I₀ cos²θ — in real time
🔮 Polarization of Light
Natural light is unpolarized — its electric field oscillates in all perpendicular planes simultaneously. A polarizer transmits only the component aligned with its transmission axis, producing linearly polarized light.
When polarized light passes through a second polarizer (analyzer)
rotated by angle θ:
I = I₀ · cos²(θ)
— Malus's Law (Étienne-Louis Malus, 1808)
Circular polarization arises when two equal-amplitude, orthogonal oscillations are 90° out of phase (±¼ wavelength retardation). Elliptical polarization is the general case. A quarter-wave plate converts linear to circular; a half-wave plate rotates the polarization direction.
Birefringent materials (calcite, quartz) have two different refractive indices for orthogonal polarizations, splitting beams and creating retardation effects used in LCD screens and optical instruments.