Refraction of light
Beginner
Bending of light at a boundary.
n₁ sinθ₁ = n₂ sinθ₂At a boundary the speed changes and the ray bends toward the normal when entering a denser medium. The frequency stays constant; wavelength changes.
A straw looks bent in water.
Bending happens because of the speed change.
In more detail
Refraction is the bending of light as it passes from one medium to another, because its speed changes. The bending depends on the refractive indices of the two media.
Real-world uses
- Eyeglasses and camera lenses rely on refraction.
- Fish appear displaced because of refraction at the water surface.
- A straw in a glass of water looks bent at the surface, because light refracts as it passes from water to air.
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Frequently asked questions
Why does light bend?
Because its speed changes at the boundary, and the wavefront turns.
Does light bend towards or away from the normal?
Towards the normal when entering a denser medium, and away when entering a less dense one.
Does refraction happen for all waves?
Yes, any wave changes direction when its speed changes, including sound and water waves.
Related topics in Optics
Mirror equation · Magnification of a mirror · Focal length and radius · Refractive index · Snell's law · Apparent depth