This innovative modern physics textbook is intended as a first introduction to quantum mechanics and its applications. Townsend's new text shuns the historical ordering that characterizes other so-called modern physics textbooks and applies a truly modern approach to this subject, starting instead with contemporary single-photon and single-atom interference experiments. The text progresses naturally from a thorough introduction to wave mechanics through applications of quantum mechanics to solid-state, nuclear, and particle physics, thereby including most of the topics normally presented in a modern physics course.