This lecture covers the behavior of optical waves in different media, discussing concepts such as energy transmission, Poynting vector, reflection, refraction, and the Fresnel equations. It explains how the intensity of light is affected by interfaces, total internal reflection, and the use of prisms and retroreflectors. The lecture also explores the application of optical principles in devices like lenses and fibers, emphasizing total internal reflection in optical fibers and the focusing of light by lenses.