The wave undergoes refraction as it passes from propagation medium 1 to propagation medium 2
In wave physics we can say that one of the main phenomena involving two-dimensional waves is refraction. The refraction of a wave occurs at the liquid surface, when a wave passes from one propagation medium to another, that is, it passes from a region of greater depth to another region of lesser depth, or the opposite.
We can see in the figure above an example of wave refraction on the liquid surface, where there is a deviation in the wave propagation direction due to refraction, which happens when the wave passes from propagation medium 1 to propagation medium 2.
Therefore, we can conclude that the phenomenon of wave refraction occurs whenever the wave crosses the surface that separates two media in which the wave propagation speed is different.
In refraction, the frequency of a wave is the frequency of the generating source itself, that is, it remains constant. Velocity and wavelength are directly proportional, this can be proven through the equation: v = λf. Deviation in the direction of propagation of a wave will only occur if it impinges on the separating surface between the media with an inclination, that is, if it impinges obliquely.
If the wave hits perpendicularly, that is, normally, it will not be deflected in its trajectory, but its speed and wavelength will vary.
Mathematically, we can calculate the deviation suffered by a wave through the Law of Refraction or Snell-Descartes Law. That law says:
i – is the angle of incidence of the incident wave
r – is the angle of refraction of the refracted wave
n 1 – is the index of refraction of the medium 1
n 2 – is the index of refraction of the medium 2
v 1 – is the speed of propagation of the wave in medium 1
v 2 – is the propagation speed of the wave in medium 2