Refractive Index (n)
What is the refractive index?
Refractive index, also known as the refractive coefficient of a medium, is the degree to which light “travels slowly” in a material.
- Light travels fastest in a vacuum (at a speed of approximately 300,000 kilometers per second), and we define its refractive index as 1.
- If light enters materials such as water, glass, and diamond , it will travel slower, so their refractive indices are greater than 1
Definition formula of refractive index:
Optically Dense Medium and Optical Rarer Medium:
The larger the refractive index, the slower the light propagates in the medium. That is to say:
- High refractive index = slow propagation = more "optically dense" medium
- Small refractive index = fast propagation = more "optically rarer" medium
*Light will bend when light travel between mediums with different refactive index.
Refractive Index of Common Materials
| Material | Refractive index nn |
| Vacuum | 1 |
| Air | 1.0003 |
| Water | 1.33 |
| Ordinary Glass | 1.50 ~ 1.52 |
| Optical Glass | 1.60 ~ 1.90 |
| Diamond | 2.42 |