What term describes the bending of light as it moves from air into glass?

• A. Refraction
• B. Reflection
• C. Absorption
• D. Scattering

Answer: (A)

Refraction is the bending of light as it passes into a different medium because the light changes speed at the boundary. When light moves from air into glass, it slows down because glass has a higher optical density (index of refraction) than air. This change in speed alters the light’s direction, causing it to bend toward the normal (the line perpendicular to the surface) if the light hits at an angle. The underlying relation is Snell’s law: n1 sinθ1 = n2 sinθ2; since n2 is larger for glass, sinθ2 is smaller, so the refracted ray is closer to the normal than the incident ray. If light were moving from glass back into air, it would bend away from the normal.

This phenomenon is distinct from reflection (bouncing off the surface), absorption (light energy taken up by the material), and scattering (light being redirected in many directions).