Waves occur in almost all branches of physics.
We are going to study waves, but here we will not assume knowledge of physics and differential equations. We will use only assumptions about the general principles of delay, continuity, and energy conservation. The results will be directly applicable to sound waves, water waves, light in thin films, normal incident elastic waves of both pressure and shear type, electromagnetic waves, transmission lines, electrical ladder networks, and other such things. The methods can also be applied to diffusion problems. Our first main objective is to solve the problem of calculating wave fields given reflection coefficients.