Refractive Index

Refractive Index

1. Refraction is caused by the waves changing speed

   • Refraction is when waves change direction as they enter a different medium
     • Caused by a change in density from one medium to another - changes speed of the waves
   • 1 - When waves slow down they bend towards the normal
   • 2 - When light enters glass or plastic it slows down - about 2/3 air speed
   • 3 - If a wave hits a boundary at 90deg (the normal) it won't change direction, just slow down
   • 4 - When light hits a different medium (eg. plastic or glass) some of the light will pass through the new medium but some will be reflected
     • Depends on angle of incidence (the angle that it hits the medium)

2. Every transparent material has a refractive index

   • The 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, the angle of refraction r, and the 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
     • Refractive index (n) = sin i/ sin r
       • Can be rearranged to suit needs

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