This two-volume text is for new graduates on astronomy courses who need to get to grips with the physics involved in the subject. Four problem sets, averaging three problems per set, accompany each volume. The problems expand on the material covered in the texts and represent the level of calculational skill needed to write scientific papers in contemporary astrophysics. Volume I. "Radiation" deals with the emission, absorption, and scattering of radiation by matter, radiative transfer, statistical physics, classical electrodynamics, and atomic and molecular structure.