This lecture covers the concept of spatial frequencies in optics, explaining how they are related to plane waves and diffraction phenomena. It delves into the decomposition of transparency using Fourier transforms, the propagation of spatial frequencies, and the diffraction of Fresnel and Fraunhofer. The transfer function for image propagation, the Fresnel lens effect, and the 2f optical system are also discussed, along with the double Fourier transform and filtering techniques in optical systems.