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

airglass

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 raynormal

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 WaterWater n = 1.3330Pyrex n = 1.470

Stirring Rod in OilOil n = 1.474Pyrex 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.

Bent chopstick

Water Line

Air

A

B

C

Examples of refraction of light Shallower in water

O

Ireal 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.

A boy shines a torch under water as shown.Which one shows the correct path of the light ray?