Textbook in PDF format This book aims at presenting basic principles of Quantum Mechanics to graduate and postgraduate students of physics at various Universities. The text has been divided into 23 chapters for the convenience of the students. Solved examples and questions have been incorporated to enable the students in gaining a better understanding of the concepts involved. The second edition has been revised and the following topics have been included: Physical significance of spherical harmonics, field and coordinates of the field, Lagrangian formulation for the fields, commutation relations for field operators, quantisation of non-relativistic Schrödinger field, the neutral Klein Gordon field, the Dirac field, the neutral Klein Gordon field in terms of plane waves, the charged KG field, the Einstein-Podolsky-Rosen problem and the Aharonov-Bohm effect. This book aims to cover the UGC curriculum of physics for quantum physics. Designed for BSc (Hons) and MSc in Physics it will also serve as a useful text/reference for students of chemistry. The text lays emphasis on physical concepts with details of necessary mathematical steps. The salient features of the book include clear presentation of concepts student-friendly approach solved examples tables and illustrations for better understanding of the concepts and questions at the end of each chapter. This is the thoroughly revised edition which includes new topics such as Physical significance of spherical harmonics field and coordinates of the field Lagrangian formulation for the field commutation relations for field operators• quantisation of nonrelativistic Schrodinqer field• the neutral Klein Gordon field the Dirac field the neutral Klein Gordon field in terms of plane waves• the charged KG field the Einstein-Podolsky-Rosen problem and the Aharonov-Bohm Effect. Foundation of 'Quantum' - Concept Wave Mechanics Operator—Formalism The Fourier Transform, Dirac Delta Function and Wave Packets Linear Harmonic Oscillator Solution of Schrödinger Equation for Spherically Symmetric Problems Matrix Formulation of Quantum Mechanics Dirac Representation Theory Simple Harmonic Oscillator using Ladder Operators Introductory Quantum Dynamics (The Three Quantum Mechanical Pictures) Angular-Momentum The Internal Angular Momentum Total Angular Momentum Symmetries, Invariance Principles and Conservation Laws Time Independent Perturbation Theory The Variation Method The WKB Approximation Method Time Dependent Perturbation Theory Many Electron Atoms Theory of Scattering Relativistic Theory Quantization and Second Quantization The Einstein-Podolsky-Rosen Paradox The Aharonov-Bohm Effect Appendices Alternative Derivation of Uncertainty Principle Integrals Involving Gaussian Functions Tensors Legendre and Associated Legendre Functions and their Recurrence Relations Density Matrix and Density Operator The Relativistic Notations Hamiltonian in Polar Coordinates Bibliography Index