Refractive Index

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Refraction is Caused by the Waves Changing Speed

Refraction is when waves change direction as they enter a different medium. This is caused by the change in density from one medium to another - which changes the speed of the waves.

1. When waves slow down they bend towards the normal

2. when light enters glass or plastic it slows down by 2/3 of its speed when in the air

3. If a wave hits a boundary at 90* (i.e. along the normal) it it will not change direction but will slow down

4. When light hits a different medium (e.g. glass or plastic) some of the light will pass through the new medium and will be refracted but some will be reflected - it all depends on the angle of incidence (the angle the light hits the new medium)

Every Transparent Material Has a Refractive Index

1. Refractive index is the ratio of the speed of light in a vacuum to the speed of light in that medium

2. The angle of incidence, i, angle of refraction, r, and the refractive index are all linked

3. When an incident ray passes from air into another material the angle of refraction depends on the refractive index of the material:

Refractive Index (n) = sin i

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