Quantum mechanics emerged as one of the greatest discoveries in science owing to pioneering work and individual contributions of eminent scientists—Planck, Einstein, Bohr, Compton, de Broglie, Schrodinger, Heisenberg, and Dirac—over a span of three decades from 1900 to 1930. Later, path integral formalism and quantum electrodynamics came through the work of Feynman. Still later, Weinberg and Salam developed the electroweak theory. The entire spectrum of both non-relativistic quantum mechanics and relativistic quantum mechanics has been covered in this book in a simple style to be truly beneficial to all levels of students.

The book is organized into three parts. The first part describes the development of quantum theory, starting from Planck’s law to de Broglie hypothesis. The Schrodinger theory has been introduced with relevant logic. This part also includes the treatments of angular momentum, path integral formalism, two-electron systems and interaction of radiation with matter. The second part deals with relativistic quantum theory including Klein–Gordon and Dirac equations, Weyl’s neutrino theory, ending with gauge theory applied to Salam–Weinberg electroweak theory. The third part delves into the conceptual foundations of quantum mechanics, and Einstein–Bohr debate culminating in Bell’s inequality theorem. The book concludes with a discussion on three quantum interference effects in electromagnetic and gravitation fields each of which has a deep physical importance.

Throughout, the book is suitably illustrated to clarify the concepts and contains worked-out problems as well as chapter-end exercises.

This book is intended for undergraduate and postgraduate students of physics and chemistry.