Geometric optics is the study of the path of light rays through systems of lenses, mirrors, and other media. English physicist and mathematician Sir Isaac Newton's Opticks published in 1704 formalized the description of image-formation in lenses and mirrors, providing the first thorough study of geometric optics.

The law of reflection states that the angle of an incident beam is equal to its angle of reflection. A medium that allows the passage of light without a change in velocity of light is said to have index of refraction (n) where the velocity of light propagation is determined as the velocity of light in a vacuum (c) divided by the index of refraction (n).

A ray of light that propagates across the interface (boundary) of two media (materials) obeys Snell's law of refraction. The media of incoming and outgoing rays, having indices of refraction n and n, respectively...