The diagram at right illustrates the refraction of a wave as it propagates from a medium of larger wave speed into a medium of slower wave speed.
a. Use trigonometry to determine the mathematical relationship between the angle of incidence (̈θi), the angle of refraction (θr), the wavelength of the incident wave (λi), and the wavelength of the refracted wave (ιλr). Show your work.
b. Starting from the equation that you wrote above, derive a mathematical formula relating θi, θr, vi, and vr, where vi and vr are the propagation speeds of the incident and refracted wave, respectively. Show your work.