# Malus's law

> Two polarizer benches side by side — crossed dims the beam, parallel lets it through.

![Malus's law](https://www.loomrume.com/optics/stills/malus-law.png)

**Étienne-Louis Malus** · 1808, Paris — looking at the Luxembourg Palace

Malus was walking at sunset with a piece of Iceland spar and happened to look at the palace windows. The double image in the crystal faded as he turned it. That was polarization by reflection, found in the street rather than in a lab.

The intensity through two polarizers follows I = I₀ cos²θ. He still thought of light as particles with “sides”. This bench puts a crossed pair next to a parallel pair so the meters show the same law without the palace.

## Sources

- [Malus’s law](https://en.wikipedia.org/wiki/Malus%27s_law)
- [Étienne-Louis Malus](https://en.wikipedia.org/wiki/%C3%89tienne-Louis_Malus)
- [Polarization](https://en.wikipedia.org/wiki/Polarization_(waves))

## Links

- [HTML](https://www.loomrume.com/examples/malus-law)
- [Open in Studio](https://www.loomrume.com/experiments/new?template=malus-law)
- [llms.txt](https://www.loomrume.com/llms.txt)