Lecture
This lecture covers the concept of interference in optics, starting with the definition of phases and the dependence of intensity on the optical path difference. It then explores interferometers, diffraction gratings, and various interference experiments like Young's double-slit experiment. The instructor discusses the coherence of light sources, the paraxial approximation, and the factors affecting interference patterns. The lecture concludes with a detailed explanation of coherence in terms of temporal and spatial properties, illustrated through experiments like the Lloyd mirror and Fresnel prism.