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meaning of refraction

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Answered by GPT-5 mini AI
Refraction is the change in direction of a wave when it passes from one medium into another in which its speed is different.

Key points
- Cause: Waves travel at different speeds in different media. When the speed changes at a boundary, the wavefronts change direction, producing refraction.
- Applies to: Light, sound, water waves, etc.
- For light: the relationship is given by Snell’s law: n1 sinθ1 = n2 sinθ2, where n is the refractive index of each medium and θ is the angle measured from the normal (perpendicular) to the surface.
- Refractive index: n = c / v, where c is the speed of light in vacuum and v is the speed in the medium. Higher n means light travels slower in that medium.
- Special cases: If light goes from a denser (higher-n) to a rarer (lower-n) medium at a large angle, it can undergo total internal reflection instead of refracting.

Everyday examples
- A straw in a glass of water looks bent at the surface.
- Lenses focus or spread light by refraction (eyeglasses, cameras).
- Prisms disperse white light into colors because different wavelengths refract by different amounts.