Which phenomenon describes the bending of light as it passes from one medium to another?

Refraction is the phenomenon that describes the bending of light as it transitions from one medium to another, such as from air into water or from glass into air. This bending occurs due to a change in the speed of light as it enters a medium with a different optical density.

When light travels through a medium, it behaves differently depending on the medium's properties. For instance, light travels faster in air than in water, and upon hitting the water surface, it slows down, causing the light to change direction. This change in speed and direction is what constitutes refraction. The extent of bending is described by Snell's Law, which relates the angles of incidence and refraction to the indices of refraction of the two media.

Understanding refraction is essential in explaining various optical phenomena, which are critical in the fields of physics, optics, and even everyday applications like lenses in glasses or cameras.