This page discusses wave propagation in vacuum and simple media, including reflection at boundaries and waveguide behavior. It details boundary condition fulfillment in resonators and the establishmen...This page discusses wave propagation in vacuum and simple media, including reflection at boundaries and waveguide behavior. It details boundary condition fulfillment in resonators and the establishment of resonant frequencies. The latter part covers the generation and reception of waves via antennas and arrays, extending to anisotropic, dispersive, and ionized media.