This book covers important concepts and applications of contemporary physics. The book emphasizes logical development of the subject and attempts to maintain rigor in the analytical discussions. The text has been presented in a concise and lucid manner. A modern description of properties and interaction of particle is given along with discussions on topics such as cosmology, laser and applications. The concepts are illustrated by numerous worked examples. Selected problems given at the end of each chapter help students to evaluate their skills. The book with its simple style, comprehensive and up-to-date coverage is highly useful for physics students. The detailed coverage and pedagogical tools make