This classic study, available for the first time in paperback, clearly demonstrates how quantum theory is a natural development of wave theory, and how these two theories, once thought to be irreconcilable, together comprise a single valid theory of light. Aimed at students with an intermediate-level knowledge of physics, the book first offers a historical introduction to the subject, then covers topics such as wave theory, interference, diffraction, Huygens' Principle, Fermat's Principle, and the accuracy of optical measurements. Additional topics include the velocity of light, relativistic optics, polarized light, electromagnetic theory, and the quantum theory of radiation. The more difficult mathematics has been placed in appendixes, or in separated paragraphs in small type, intended to be omitted on first reading. Examples and/or references follow each chapter to assist the student in absorbing the material and to suggest additional resources.