# Young–Helmholtz theory

> postulated existence of three photoreceptor types in the eye

**Wikidata**: [Q1257777](https://www.wikidata.org/wiki/Q1257777)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Young–Helmholtz_theory)  
**Source**: https://4ort.xyz/entity/young-helmholtz-theory


## References

1. Freebase Data Dumps. 2013