Absolute Refractive Index of a Medium - Definition

Refractive Index of a Medium in Absolute Terms:The ratio of the speed of light in a vacuum to the speed of light in a given medium is known as the absolute refractive index. There is always more than one. The absolute refractive index is expressed as $n=\frac{c}{v}$ if c is the speed of light in a vacuum and v is the speed of light in the chosen medium.