ABSTRACT
All of geometrical optics can be derived from the Fermat’s principle, which states that, given a light ray between two points and its travel time between them, any adjacent path close to it should have the same travel time. Being a principle, it is not demonstrated, but accepted as being true and used to derive the entire mathematical framework of geometrical optics. It is, however, possible to infer why it describes the behavior of light by analyzing refl ection and refraction.
