This textbook offers a clear and engaging introduction to Modern Physics. The focus of this book is on building a strong conceptual framework, guiding students from fundamental principles to complex topics. This new edition enriches the contents by adding the Complimentarity Principle, Ehrenfest Theorem and Macroscopic Quantum Tunnelling a detailed discussion of radioactive decay equilibrium. The chapter on Cosmology has been refreshed covering the Standard Model of cosmology, Hubble tension, Gravitational Waves, LIGO and the James Webb Telescope.