Refraction is the bending of a wave, such as light, as it passes from one medium to another with differing properties. This change in direction occurs because the wave's speed alters as it enters a medium with a different optical density. The degree of bending is dictated by the relative speeds and the indices of refraction of the initial and final media. This phenomenon is fundamental to optics and is utilized in various technologies, including the function of lenses and prisms, which rely on controlled refraction to manipulate light paths. Understanding refraction is critical for the study of how electromagnetic waves propagate through materials, forming the basis for many imaging and sensing technologies.