# Newton prism

> White light through a triangular prism fans into a spectrum — Newton’s classic demo.

**Isaac Newton** · 1666, Cambridge — Opticks, 1704

Newton darkened his rooms at Trinity, let a sunbeam through a small hole, and put a triangular glass prism in the path. The round white spot on the wall became an oblong spectrum. That was already enough to argue that sunlight is mixed, not a pure colour that glass “stains”.

The experimentum crucis used a second prism: one colour from the first fan, sent through again, stayed that colour. The glass was not painting the light. White light was already a pile of colours, and the prism only sorted them by how much each bent.

He sat on the result for years and published it in Opticks in 1704. This bench is the first half of that demo — white in, a fan out — so you can drag the prism and watch the order of the colours stay put.

## Sources

- [Opticks](https://en.wikipedia.org/wiki/Opticks)
- [Dispersion](https://en.wikipedia.org/wiki/Dispersion_(optics))
- [Isaac Newton](https://en.wikipedia.org/wiki/Isaac_Newton)

## Links

- [HTML](https://www.loomrume.com/examples/newton-prism)
- [Open in Studio](https://www.loomrume.com/studio?template=newton-prism)
- [llms.txt](https://www.loomrume.com/llms.txt)