Modern physics began in 1900 with Max Planck’s discovery of the role of energy quantization in blackbody radiation, a revolutionary- idea soon followed by Albert Einstein’s equally revolutionary theory of relativity and quantum theory of light. Students today must wonder why the label “modern” remains attached to this branch of physics. Yet it is not really all that venerable: my father was born in 1900, for instance, and when 1 was learning modern physics most of its founders. including Einstein were still alive; I even had the privilege of meeting a number of them, including Heisenberg, Pauli, and Dirac. Few aspects of contemporary science—indeed, of contemporary life—are unaffected by the insights into matter and energy provided by modern physics, which continues as an active discipline as it enters its second century.
This book is intended to be used with a one-semester course in modem physics for students who have already had basic physics and calculus courses. Relativity and quantum ideas are considered first to provide a framework for understanding the physics of atoms and nuclei. The theory of the atom is then developed with the emphasis on quantum-mechanical notions. Next comes a discussion of the properties of an aggregate of atoms, which includes a look at statistical mechanics. Finally, atomic nuclei and elementary particles are examined.