# Right-angle prism

> Two right-angle prisms turn the beam by total internal reflection — white light lands on the screen.

![Right-angle prism](https://www.loomrume.com/optics/stills/right-angle-prism.png)

**Ignazio Porro** · 1854 — Porro’s binocular prism

A right-angle glass prism can turn a beam by total internal reflection — no silver to tarnish. Porro stacked two of them in 1854 so a binocular could be short and still erect the image. The Porro prism binocular is that pair in a Z.

This bench is the simpler turn: two prisms, white through, a screen at the end. TIR only holds if the hypotenuse is clean and the angle is right. Tilt past that and the beam starts to leak.

## Sources

- [Porro prism](https://en.wikipedia.org/wiki/Porro_prism)
- [Total internal reflection](https://en.wikipedia.org/wiki/Total_internal_reflection)

## Links

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