In Module 1-3, Basic Geometrical Optics, we made use of light rays to demonstrate reflection and refraction of light and the imaging of light with mirrors and lenses. In this module, we shift the emphasis from light rays to light waves - from geometrical optics to physical optics. In so doing, we move from a concern over the propagation of light energy along straight-line segments to one that includes the spreading of light energy - a fundamental behavior of all wave motion.
With wave optics - commonly referred to as physical optics - we are able to account for important phenomena such as interference, diffraction, and polarization. The study of these phenomena lays the foundation for an understanding of such devices and concepts as holograms, interferometers, thin-film interference, coatings for both antireflection (AR) and high reflection (HR), gratings, polarizers, quarter-wave plates, and laser beam divergence in the near and far field.