What is refraction in optics?

Refraction is defined as the bending of light as it travels from one medium to another, which occurs due to changes in the speed of light. When light enters a medium with a different density, such as from air into water, it changes speed, resulting in a change in direction. This bending effect is governed by Snell's law, which quantitatively relates the angles of incidence and refraction to the indices of refraction of the two media.

Understanding refraction is crucial in various applications, including the design of lenses, the effect of prisms, and phenomena such as the apparent bending of a straw in a glass of water. The ability of light to change direction while crossing boundaries between different materials underlies many optical devices and natural occurrences.