Refraction 1
When light waves pass from air into a more dense material such as water, glass, plastic etc. they slow down.
The ratio of their velocity in air (or more correctly in free space) to their velocity in the material is called its refractive index.
| Refractive index = velocity in free space (usually taken as air)/
velocity in the material
|
| Material |
Refractive index |
Material |
Refractive index |
| Diamond |
2.42 |
Glycerol |
1.47 |
Ruby |
1.76 |
Water |
1.33 |
| Glass |
1.5 |
Air at STP |
1.000 298 |
The law relating the angle of incidence (i), the angle of refraction (r) and the refractive index (n) is known as Snell's Law.
Snell's law states that:
| Refractive index (n) = sin i/sin r |
The absolute refractive index of a material is that compared to free space which is given a refractive index of 1.000.
The values given in the table are absolute refractive indices.
