Here's why:
* Light travels at different speeds in different mediums. Light travels fastest in a vacuum, and slower in materials like air, water, or glass.
* The change in speed causes the light to bend. When light enters a denser medium (like from air to water), it slows down and bends towards the normal (an imaginary line perpendicular to the surface). When light enters a less dense medium (like from water to air), it speeds up and bends away from the normal.
This bending of light is responsible for many everyday phenomena, including:
* Seeing objects underwater: The light from an object underwater bends as it enters the air, making the object appear closer to the surface than it actually is.
* Rainbows: Sunlight is refracted by water droplets in the atmosphere, separating the light into its different colors.
* The appearance of a straw in a glass of water: The straw appears bent because light from the straw bends as it passes from the water into the air.
Refraction is a fundamental principle in optics and is used in many optical devices, such as lenses, prisms, and telescopes.
