How does refraction occur in waves?

Refraction occurs in waves primarily due to the change in speed as they transition from one medium to another. When waves move from one material—like air—into another, such as water or glass, their speed is affected by the physical properties of the new medium. This change in speed causes the waves to change direction.

For example, when light travels from air into water, it slows down. This reduction in speed results in the bending of the light path at the boundary between the two media, leading to the phenomenon known as refraction. The degree of bending can be described by Snell's Law, which relates the angles of incidence and refraction to the speeds of light in the respective media.

In contrast, traveling through a single medium without changing speed or direction does not produce refraction. Additionally, changes in frequency without an accompanying speed change represent different concepts, such as Doppler Effect, rather than refraction. Thus, the nature of refraction is fundamentally tied to the interaction between different media and the change in wave speed that this interaction induces.