Refraction
In GCSE physics curriculum, by definition, refraction is when waves change direction as they enter a different medium caused by a change in density which changes the speed of the waves.
- When waves slow down, they bend towards the normal.
- When light enters glass or plastic, it slows down.
- If a wave hits a boundary at 90 degrees (I.e. along the normal line) it will not change direction but it will still slow down.
- When light hits a different medium (e.g. Plastic or glass) some of the light will pass through the medium but some will be reflected. It all depends on the angle of incidence (the angle it hits the medium).
In GCSE physics, every transparent material has a refractive index.
Refractive index of a medium is the ratio of speed of light in a vacuum to speed of light in that medium.
The angle of incidence, i, angle of refraction, r, and refractive index, n, are all linked.
When an incident ray passes from air into another material, the angle of refraction of the ray depends on the refractive index of the material.
You need to remember refractive index (n) = sin i / sin r in GCSE physics.
So, if you know any two of n, i or r, you can work out the missing one.
End of this topic!
Drafted by Gina (Physics)