What do we call the bending of light rays as they enter a different medium?

The bending of light rays as they enter a different medium is referred to as refraction. Refraction occurs when light travels through different materials, such as from air into water or glass. This bending happens because light travels at different speeds in different media; when it passes from one medium to another, its speed changes, causing the change in direction.

For instance, when light enters water, it slows down compared to when it was in the air. The change in speed causes the light rays to bend at the interface of the two media. This principle is fundamental in optics and is used in lenses and other optical devices to manipulate light.

Absorption involves the light being absorbed by the material, leading to a loss of energy, and therefore does not entail bending. Reflection refers to light bouncing back when it encounters a surface, rather than passing through a different medium. Diffraction is the bending and spreading of waves around obstacles or through openings, which is not specific to changes in medium but rather the wave nature of light.