Book excerpt: Introduction to Modern Physics, Second Edition is a 16-chapter text that discusses the principles of modern physics. This book deals first with the basic topics of modern science including the atomic nature of matter and electricity; the theory of relativity; the old quantum theory; waves and particles; and the Schrödinger equation. The subsequent chapters cover other general topics of molecular spectra, superconductivity, and the biological effects of radiation, illustrating the fundamental quantum theory of angular momentum and the harmonic oscillator. The remaining chapters explore the properties of nucleus, nuclear transformation, and interactions of particles. This book is an invaluable source for undergraduate quantum mechanics students.