When light passes from one medium to another (such as from air to water or from glass to air), its speed changes, which causes the light to bend. This bending is called refraction and is governed by Snell’s Law.
Here’s how light behaves:
- Speed changes:
- In a denser medium (like glass or water), light slows down.
- In a less dense medium (like air), light speeds up.
- Direction changes:
- When light enters a denser medium, it bends toward the normal (the imaginary line perpendicular to the surface).
- When light enters a less dense medium, it bends away from the normal.
- Wavelength changes:
The wavelength of light decreases in a denser medium, but its frequency remains the same. - Partial reflection:
At the boundary, some light may also reflect back into the original medium, depending on the angle and surface.
This behavior explains many optical effects, such as the bending of a straw in water, the formation of rainbows, and how lenses focus light.