''Modern Physics'' is the most up-to-date, accessible presentation of modern physics available. The book is intended to be used in a one-semester course covering modern physics for students who have already had basic physics and calculus courses. The balance of the book leans more toward ideas than toward experimental methods and practical applications because the beginning student is better served by a conceptual framework than by a mass of details. The sequence of topics follows a logical, rather than strictly historical, order. 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, and followed by a discussion of the properties of aggregates of atoms, which includes a look at statistical mechanics. Finally atomic nuclei and elementary particles are examined.