1. Geometrical optics framework

1.1 Context

Geometrical optics is an approximation that explains everyday observations of light in the form of rays. Establishing a realistic model of these light lines was controversial in the past, but today it is accepted that the equations of electrodynamics provide an acceptable solution for describing such phenomena. Periodic variations of an electromagnetic potential in time and space generate both an electric and a magnetic field, which contribute to the propagation of light waves. However, only the electric field is the focus of attention, as it alone sensitizes the optical sensors measuring luminous flux. In addition, it should be noted that the frequencies present in visible radiation are very high, on the order of several hundred terahertz. Taken together, these aspects...