Ray optics and geometrical optics in fact contain exactly the same physical content, expressed in different fashion Ray matrices orABCD matrices are widely used to describe the propagation of geometrical optical rays through paraxial optical elements such lenses curved mirrors and ducts. These ray matrices also turn out to be very useful for describing a large number of other optical beam and resonator problems, including even problems that involve the diffractive nature of light• Ray optics and geometrical optics in fact contain exactly the same physical content, expressed in different fashion. • Ray matrices or “ABCD matrices” are widely used to describe the propagation of geometrical optical rays through paraxial optical elements, such lenses, curved mirrors, and “ducts”. These ray matrices also turn out to be very useful for describing a large number of other optical beam and resonator problems, including even problems that involve the diffractive nature of light