This lecture covers topics such as the Jaynes-Cummings model, dispersive regime of cavity QED, atom passing through the cavity, and examples related to the birth, life, and death of a photon. It delves into the energy shifts, eigenstates, and eigenenergies in the context of cavity QED, providing insights into the dispersive regime and the double QND Hamiltonian. The lecture also discusses the spectral response of the double QND Hamiltonian and the resolution of photon number states in a superconducting circuit.