Geometrical Optics

The rigorous way of treating light is to accept its electromagnetic wave nature and solve Maxwell’s equations. However the number of configurations for which exact solutions can be found is very limited and most practical cases require approximations.

Based on the specific method of approximation, optics has been broadly divided into two categories, these being geometrical optics (ray optics) treated in this chapter and wave optics (physical optics) already treated in Chapter 3. The approximation used in geometrical optics puts the emphasis on finding the light path; it is especially useful for tracing the path of propagation in inhomogeneous media or in designing optical instruments. The approximation used in physical optics, on the other hand, puts the emphasis on analyzing interference and diffraction and gives a more accurate determination of light distributions.