What do we call the change in direction of light as it passes from one medium to another?

The change in direction of light as it passes from one medium to another is referred to as refraction. This phenomenon occurs due to the change in the speed of light when it enters a different medium, which has a different optical density. For example, when light travels from air into water, it slows down and changes direction, causing the bending effect that characterizes refraction.

In addition to refraction, there are other terms related to the behavior of light. Reflection refers to the bouncing back of light when it hits a surface. Dispersion involves the separation of light into its constituent colors, often observed in prisms, and diffusion is the scattering of light as it passes through a medium, causing it to spread out. Understanding these definitions reinforces why refraction specifically refers to the bending of light when it transitions between different materials, making it the correct answer in this context.