To refract means to bend light (or other waves, like sound) as it passes from one material into another. When a beam of light travels from air into water, it refracts, changing direction at the boundary between the two substances. This bending happens because light travels at different speeds through different materials.

You've seen refraction if you've ever noticed how a straw in a glass of water looks broken or bent at the surface. The straw isn't actually bent: the light bouncing off the underwater part refracts as it exits the water and enters the air, making your eyes see the straw in a slightly different position than it really is.

Refraction is what makes rainbows possible. When sunlight enters a raindrop, it refracts, splitting into its component colors (red, orange, yellow, green, blue, indigo, violet). Each color bends by a slightly different amount, spreading them out into the beautiful arc we see in the sky.

Eyeglasses and contact lenses work by refracting light in precise ways to help people see more clearly. Cameras, telescopes, and microscopes all use carefully shaped glass lenses that refract light to magnify distant stars or tiny cells. Understanding refraction helped scientists and inventors create tools that let us see things we could never observe with our eyes alone.