Optics: Lectures on Theoretical Physics, Volume IV focuses on the study of optics, particularly on the refraction and reflection of light. Composed of six chapters, the book focuses first on the historical outline of geometrical, physical, and physiological optics. This discussion is followed by the review of basic principles of ideal and natural light and Fresnel's equations on reflection and refraction of light. The optics of moving media and sources is discussed next. This topic covers Doppler effect, the Michelson experiment, and the quantum theory of light. The theory of dispersion is also presented, as well as the ultraviolet resonance, anomalous dispersion, Normal Zeeman effect, and the wave mechanical theory of dispersion. The next part of the book covers crystal optics, including active crystals and fluids, the problem of double refraction, and the optical symmetry of crystals. The theory of diffraction and related experiments are also noted. Numerical analyses and representations are presented in this consideration. Considering the value of the discussions, the readers, including scholars and readers interested to study the physics involved in optics, will find this book a vital source of data.