Which phenomenon describes the bending of light rays as they pass through different mediums?

The bending of light rays as they pass through different mediums is known as refraction. This phenomenon occurs due to the change in speed of light as it moves between materials with different optical densities. When light enters a medium such as water from air, it slows down and bends towards the normal line (an imaginary line perpendicular to the surface at the point of entry). Conversely, when light exits a denser medium to a less dense one, it speeds up and bends away from the normal. This bending effect is critical in various applications, including lenses in glasses, the design of optical instruments, and understanding phenomena like rainbows. Understanding refraction also distinguishes it from other processes such as reflection, where light bounces off a surface, or absorption, where light is taken in by a material rather than passing through it.