Refraction
A wave changes speed, and usually direction, when it passes from one material into another. Light bends towards the normal when it slows down.
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Analogy
A car driving from road onto sand: the wheel that hits the sand first slows, so the car swings round.
In practice
A straw looks bent in a glass of water. Lenses use refraction to focus light.
Practice
Flashcards
- What is refraction?A wave changing speed, and usually direction, as it enters a different material.
Questions people ask
Why does light bend when it enters glass?
Light travels more slowly in glass than in air. When a ray meets the glass at an angle, one side of the wave slows down first, and that swings the wave's direction. It bends towards the normal on entering the glass and away from the normal on leaving.
Why does a swimming pool look shallower than it is?
Light from the bottom bends away from the normal as it leaves the water into air. Your brain assumes light travels in straight lines, so it traces the rays back to a point higher up. The pool bottom appears closer to the surface than it really is.