This lecture covers the concept of wave packets, their relation to Fourier transforms, and the dispersion of group speed. It explains how different frequencies in wave packets result in delays, the propagation of wave packets in dispersive media, and the effects of dispersion on pulse width. The instructor discusses the transformation of wave packets in series, the impact of frequency modulation on wave packets, and the potential for superluminal group speeds. The lecture also delves into interference phenomena, coherence effects on intensity, and the conditions for correct interference. Additionally, it explores diffraction of light, Young's experiment, and the principles of interferometry.