This lecture covers the fundamentals of photochemical reactions, including photo-dissociation, rearrangements, addition, substitution, and redox reactions. It also delves into the thermodynamics of photoredox reactions, charge separation, electron transfer processes, and the dynamics of electron transfer. The instructor explains the concepts of activation energy, Marcus theory, and the Marcus vs. Tafel equation, providing insights into the kinetics and energetics of light-induced electron transfer.