Lecture
This lecture discusses a physical experiment involving a metal plate illuminated by ultraviolet light. The light energy is sufficient to extract electrons from the plate, creating a positive charge on the plate due to the negatively charged electrons leaving. An electric field is then generated, pulling the electrons back towards the plate to balance the photoelectric effect. The energy balance is analyzed, considering the energy required to extract an electron (work function) and the opposing energy from the electric field. The concept of equilibrium is explained, where electrons leaving and returning to the plate reach a balance, similar to a chemical reaction in kinetics.