What is the term for the bending of light when it passes from one transparent material to another with a different refractive index?

The bending of light that occurs when it transitions from one transparent material to another with a different refractive index is referred to as refraction. This phenomenon is fundamentally important in optics and is governed by Snell's Law, which quantifies the relationship between the angles of incidence and refraction and the refractive indices of the two media involved.

When light travels through different materials, its speed changes, which causes it to change direction at the interface between those materials. For example, when light passes from air into water, the difference in refractive index between air and water results in the light bending towards the normal line of incidence. The concept of refraction is utilized in various optical devices, including lenses and fiber optic cables, where controlling light paths is crucial for proper function.

In contrast, reflection involves the bouncing back of light from a surface without altering its medium, and diffraction is the spreading of light waves when they encounter an obstacle or an aperture. Transmission refers to the passage of light through a material without being absorbed or reflected, but it does not imply any change in the light’s direction. Therefore, refraction specifically describes the change in direction due to the change in medium and refractive index, making it the correct term for this phenomenon.