This textbook has been conceptualised to meet the needs of B.Sc. Second Semester students of Physics as per Common Minimum Syllabus prescribed for all Uttar Pradesh State Universities and Colleges under the recommended National Education Policy 2020. Designed strictly as per the syllabus, the first part of the textbook comprehensively covers the theory paper, Thermal Physics & Semiconductor Devices, which discusses important topics such as laws of thermodynamics, kinetic theory of gases, theory of radiation, DC & AC circuits, semiconductors & diodes and transistors. The second part of the textbook systematically covers the practical paper, Thermal Properties of Matter & Electronic Circuits, to help students achieve solid conceptual understanding and learn experimental procedures.