Photo acceleration has dominated the theoretical plasma physics area in recent years and has found application in all subjects where waves in continuous media are studied - plasma physics, astrophysics, and optics. This theory will provide a modern understanding of photon interaction with matter, helping to develop novel accelerators based on laser-plasma interactions, new radiation sources, and even new models for astrophysical objects. Written by a major player in the field, this book describes the general theory of photo acceleration, which allows fluid, kinetic, quantum, and classical electrodynamical approaches to be formulated. It includes examples from plasma physics, cosmology, fiber optics, mathematical physics, particle accelerator physics, and radiation physics.