Refraction

light · waves · physics · bending

Waves bend when moving. When any wave, whether light, sound, or water, travels from one material to another, it changes speed and bends. The bendier the speed change, the more the wave twists direction.

The straw illusion. When you look at a straw in a glass of water, it appears to bend or break at the water line. This is refraction of light, making your eyes see something that isn't really there.

Light bends the most. Light refraction is the most common type we notice in everyday life, which is why it's so important in glasses, cameras, and rainbows.

Sound refracts too. Sound waves also refract when moving between different materials, which is why pools sound different underwater than above the surface.

Speed decides the bend. The amount a wave bends depends on how much the wave speed changes when it enters a new material. Bigger speed changes cause bigger bends.