. Optical systems. Optical systems are modeled as rays, waves, or particles. The wisest choice for the physical model is the one that provides
the simplest accurate representation of the relevant physics of the system. This seminar focuses on perhaps the simplest
physical modeling for optical systems, namely the use of rays. Ray-based light propagation models have a significant and
broad set of applications that can involve refraction, reflection, polarization, wave propagation, radiometry, diffraction,
and scattering. First, the seminar establishes the physical basis for the use of rays for modeling optical systems. Second, a
number of examples are shown that include space telescopes, modern illumination systems, mobile phone camera lenses,
spectrometers, and zoom lenses. Third, current topics of research using rays in beam propagation and polarization analysis
are discussed. The goal for seminar participants is to gain an appreciation of the power of a simple light propagation model
to solve complex problems, provided the ray approximation is applicable.