if you put a pencil in a cup of water, it looks as if it is broken and larger in the water. This is because light waves

When light enters from air to water i.e. it is moving from rarer to denser medium, it changes its original path as there is a change of speed of light and deflects itself towards the normal. This is known as the refraction of light and this is why a pencil in a cup of water looks as if it is broken and larger.

Explanation:

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