Which term describes the change in speed and possible change in direction of light as it travels from one material to another?

• A. The light returned when it hits a surface or a boundary between two different materials.
• B. The change in speed and possible change in direction of light as it travels from one material to another.
• C. The total distance light travels in air.
• D. The relative size of bright and dark areas.

Answer: (B)

Refraction is the change in speed and direction of light as it travels from one material to another. This happens because different materials have different optical densities, described by their refractive indices. When light enters a medium with a higher refractive index, it slows down and bends toward the normal; when it enters a medium with a lower refractive index, it speeds up and bends away from the normal. The amount of bending is governed by Snell's law, which links the angles of incidence and refraction to the two media's indices of refraction. This term precisely matches the described phenomenon. The other options refer to related ideas—reflection (light bouncing off a boundary), distance light travels in air, and brightness patterns—not the change in speed and direction across a boundary.