Malus’s Law Calculator

Find transmitted light intensity through a polarizer using Malus’s Law.

Incident intensity (I₀)

W/m²

Angle between polarizer axes

deg

Malus’s Law

Malus’s Law describes how the intensity of polarized light changes as it passes through a second polarizer (an analyzer): I = I₀cos²(θ), where I₀ is the incident intensity and θ is the angle between the transmission axes of the two polarizers.

When the axes are aligned (θ=0°), all the light passes through. When they’re perpendicular (θ=90°), transmission drops to zero. This relationship is a cornerstone of polarization optics and is used in everything from photography filters to LCD screens.

Last reviewed August 2026