Question

When monochromatic light is incident on a surface separating two media, why does the refracted light have the same frequency as that of the incident light?

Answer 1

The frequency and time period of an electromagnetic wave depends only on the source which produces it. The frequency is independent of the medium through which it travels. But the speed and wavelength depend on the medium through which the wave travels. Because of this, the frequency and time period of sound wave does not change due to change in medium.