# Refraction occurs at a boundary The speed of light must change at the boundary The angle of the light ray is measured from the normal, as was the case.

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Refraction occurs at a boundary The speed of light must change at the boundary The angle of the light ray is measured from the normal, as was the case with reflection

If the speed slows across the boundary, the refracted angle will be smaller – the light ray will bend toward the normal. If the speed increases across the boundary, the light ray will bend away from the normal

Refraction is the bending of light when it enters from one transparent medium into another. It is caused by the different speeds of light in different media. The greater the optical density of the medium, the slower the speed of light.

Incident ray Refracted ray Emergent ray Angle of incidence Angle of refraction normal Angle of emergence

Laws of Refraction 1.The incident ray, the refracted ray and the normal all lie in the same plane. 2.For two particular media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant. (Snell’s Law )

Refractive Index When light passes from vacuum (or air) into a given medium (eg. water), the constant ratio is known as the refractive index, n, for that medium. Angle of incidence Angle of refraction

MediumIndex of refraction = n Vacuum 1 Water 1.33 Lucite 1.5 diamond 2.4

From more dense to less dense

 Swimming pool and ponds appear shallower than it really is.  Object is at a deeper depth than where it appears to be.  Bent objects in liquids

Notice that the fish appears more shallow to the person.

On a hot summer day, as you drive down a road, you see what appears to be the reflection of an oncoming car in a pool of water. The pool, however, disappears as you approach it. Mirage s Refraction of Light

Mirages The mirage is the result of the Sun heating the road. The hot road heats the air above it and produces a thermal layering of air that causes light traveling toward the road to gradually bend upward. This makes the light appear to be coming from a reflection in a pool.

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