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Refraction is the bending of a wave when it enters a substance where its speed is different.

air glass normal incident ray angle of refraction angle of incidence refracted ray

air glass e.g. from air to glass Light is bent towards the normal. incident ray normal refracted ray From a less dense to a denser substance

air water From a denser to a less dense substance e.g. from water to air Light is bent away from the normal. incident ray refracted ray normal

When light hits a different surface than what it had been traveling in, some light is reflected and some is refracted (bent). Light passes through substances at different speeds, causing it to bend.

The index of refraction measures the speed at which light moves through the substance. The more that light is bent (refracted) as it passes through a substance, the higher the index of refraction of the substance.

Stirring Rod in Water Water n = Pyrex n = Stirring Rod in Oil Oil n = Pyrex n = 1.470

Refraction of Light by Water The index of refracton for water is 4/3, meaning that light travels 3/4 as fast in water as it does in vacuum.index of refracton

Bent chopstick

Water Line Air A B C

Examples of refraction of light Shallower in water O I real depth

‘When hunting a fish under water, you should aim your spear directly at the fish.’ Do you agree? Yes, of course. No, because the fish is actually located somewhere else. No, because size of objects changes when they are put under water.