Unpolarized light carries equal energy in every transverse E-field direction. An ideal polarizer transmits only the field component parallel to its transmission axis, so it always halves unpolarized intensity: I1 = ½·I0. A second polarizer (the analyzer), set at angle θ relative to the first, then applies Malus's Law:
I2 = I1 · cos²(θ) = ½ · I0 · cos²(θ)
At θ = 0° the analyzer is aligned with P1 and passes the full I1. At θ = 90° ("crossed polarizers") cos²(90°) = 0 and no light reaches the screen at all — that's the "Crossed" preset. The polar plot on the right traces cos²(θ) as a function of angle; the marker on it shows the current operating point.
- Linear mode animates a single oscillating E-field vector.
- Circular mode animates two equal-amplitude components 90° out of phase, tracing a circle — the polarizer still measures only the projection onto its axis, so Malus's Law still governs the analyzer stage.
- Elliptical mode uses unequal amplitudes for the two components — the general case.