Natural Science (NATS) 1525 Practice Test

Refraction is the bending of light as it moves from one medium into another with a different optical density, which changes its speed. When light crosses a boundary, it must slow down or speed up, and this change in speed makes its path tilt instead of continuing straight, following Snell’s law. That’s why a straw in water looks bent at the surface—the light is slowing as it enters the water and changes direction.

The other possibilities describe different light behaviors: bouncing off a surface is reflection, not refraction; light absorption is when light energy is taken up by the material; and light emission is light produced by a hot object or other source.