Malus Law⚠ unverified
Physics / Optics · Compute the transmitted intensity of polarized light via Malus's law
Parameters
| Input | Symbol | Unit | Default | Description |
|---|---|---|---|---|
| I0 | I0 | W/m**2 | 1.0 | Incident light intensity |
| theta | θ | — | 1.0 | Angle between the polarizer axis and the light polarization, in degrees |
| Output | Symbol | Unit | Description |
|---|---|---|---|
| result | I | W/m**2 | Transmitted intensity, in watts per square metre (W/m**2) |
The science & history
Understanding the Parameters
-
$I_0$ — for unpolarized light into a polarizer, first take $I_0/2$ then apply Malus to a second polarizer.
-
$\theta$ — radians in the solver; $\theta = 0$ full transmission; $90^{\circ}$ extinction.
- $I$ — never negative; zero at crossed polarizers (ideal).
Derivation (Approaching a Proof)
Project $\mathbf{E}$ onto the transmission axis: $E = E_0\cos\theta$. Intensity $\propto |E|^{2}$ gives $\cos^{2}\theta$.
History
Étienne-Louis Malus (1808); basis of polarimetry and LCD polarization control.
Related Concepts: Brewster Angle, Fresnel Reflection
Notes: Registry calculator malus-law (unverified). Ideal polarizer; $\theta$ in radians.