During which process can a wave slow down?

A wave can slow down during the process of refraction. Refraction occurs when a wave passes from one medium into another, causing a change in its speed due to the different properties of the two media. For example, when light travels from air into water, it slows down because water is denser than air. This change in speed results in the wave bending at the boundary between the two media.

This phenomenon is significant in various applications, such as lenses and optical systems, where controlling the wave speed and direction is essential for focusing light or creating images. Understanding refraction is crucial because it highlights the interplay between wave properties and material characteristics, which is a fundamental concept in physics.