Theodoric of Freiberg's theory of the rainbow
Teoría del arcoíris de Teodorico de Freiberg
- Date
- c. 1304-1311 · confidence high
- Place
- Freiberg, Saxony, Germany
- Credited to
- Theodoric of Freiberg
- Field
- Communication
⚠️ Disputed: the sources disagree.
What was discovered
Using water-filled glass spheres, Theodoric shows that each drop refracts, reflects and refracts the light again, and that the secondary bow arises from two internal reflections. It is the correct geometrical explanation of the rainbow, found independently of al-Farisi.
The treatise De iride was written c. 1304-1311 at the request of the Dominican Order; the place is uncertain (Freiberg was his hometown). It coincides with al-Farisi's work, which he could not have known.
What it led to
- the drop optics of Descartes and Newton
- the experimental method with physical models
- study of the rainbow's colours