Black Body Radiation: Principles and Applications

This lecture discusses the concept of black body radiation, starting with Planck's law, which describes the spectrum of emission from a black body. The instructor explains how the total power emitted is proportional to the fourth power of the temperature, introducing the Stefan-Boltzmann constant. Wien's law is also covered, illustrating how the maximum emission wavelength inversely correlates with temperature. The spectral characteristics of black bodies at various temperatures are analyzed, showing how they shift from infrared to visible light as temperature increases. The definition of a black body is clarified, emphasizing that its emission depends solely on temperature and size, with no reflection or transmission. The lecture concludes with a simplified derivation of the Planck equation, discussing photon energy, occupancy probability, and the relationship between wavelength and emission. This comprehensive overview provides a foundational understanding of black body radiation and its significance in optical detection.