The ratio of the speed of light in a vacuum to its speed in a specific medium.
Refractive index is also referred to as refraction index or index of refraction. The speed of light in a medium depends on the properties of the medium. In electromagnetic waves, the speed is dependent on the optical density of the medium. Optical density is the tendency of the atoms in a material to restore the absorbed electromagnetic energy. The more optically dense material is, the slower the speed of light. One such indicator of the optical density of a medium is the refractive index.
The refractive index is dimensionless. It is a number that indicates the number of times slower than a light wave would be in the material than it is in a vacuum. The refractive index, represented by symbol n, is the velocity of light in vacuum divided by the velocity of light in a medium. The formula of the refractive index is as follows:
\(n = \frac{c}{v}\)
Where,
n is the refractive index
c is the velocity of light in a vacuum (3 × 108 m/s)
v is the velocity of light in a substance
