On the Rainbow, a Robert Grosseteste's Treatise on Optics

Abstract

On the Rainbow is one of the short scientific treatises written by Robert Grosseteste. The Latin title is De Iride. In the first part of this treatise, we can find a discussion on reflection and refraction of light, described in the framework of the geometrical optics. In the second part, Grosseteste is writing about the rainbow and how its colors are created.