Translations:Reflection and refraction – book/2/en

When an elastic wave strikes an interface separating two media of different physical characteristics, a reflected wave is created. The reflected wave is present in the same medium as the incident wave, and therefore, they will coexist. The incident wave carries energy toward the interface, whereas the reflected wave carries energy away from it. The energy in the reflected wave necessarily must be derived from the incident wave. This does not imply, however, that all of the incident energy is reflected, because a part of it can be refracted (as a refracted wave) into the second medium. The geometric theory is incapable of determining how the energy in the incident wave is distributed between the reflected ray and the refracted ray, but it can determine a geometric relationship between the angles involved. The angular relationship between the incident ray and the reflected ray now will be derived with an application of Huygens’ principle (Figure 12).