Lesson 3 of 7

Refraction

Goal: Describe refraction.

Puzzles for this lesson

Word search0 of 8 found Crossword0 of 41 letters

A pencil standing in a glass of water. It seems to be broken where it meets the surface of the water

Light changes direction when it crosses, at an angle, from one transparent material into another. This is refraction.

Into glass or water: towards the normal. Light travels more slowly in glass and in water than in air. As it slows down, it bends towards the normal.
Out into air: away from the normal. The light speeds up again.
Along the normal: no bending. The ray goes straight on.

Why a pool looks shallow: light from the coin bends away from the normal as it leaves the water. Your brain assumes that the light has come in a straight line, so you see the coin higher up than it really is.

Your turn

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Check yourself

I can say which way light bends on entering glass or water.I can explain why a pool looks shallower than it is.

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Key words in this lesson

Ray A straight line with an arrow that shows the path of light

Normal A line at 90° to a surface, from which angles are measured

Refraction A change in the direction of light as it enters a new material

Transparent Lets light through, so you can see clearly through it

For teachers: AQA 3.4.2 · Pearson Edexcel 38.3 · Cambridge 8Ps.02