Page "Optics" Paragraph 22

Geometry of reflection and refraction of light raysGeometrical optics, or ray optics, describes the propagation of light in terms of " rays " which travel in straight lines, and whose paths are governed by the laws of reflection and refraction at interfaces between different media.

These laws were discovered empirically as far back as 984 AD and have been used in the design of optical components and instruments from then until the present day.

They can be summarised as follows: