Absolute Refractive Index

…Here, n _III is called the relative index of refraction. In the case of light, the relative index of refraction when the medium I on the incident side is a vacuum is called the absolute refractive index, or simply the refractive index, and is usually expressed as n . This is the ratio of the speed of light c in a vacuum to the speed v of light in a substance, n = c / v , and the relative refractive index is the ratio of the refractive index n _II of the medium II on the transmitting side to the refractive index n _I of the medium I on the incident side. …

*Some of the terminology used to refer to "absolute refractive index" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…ここでn_IIIを相対屈折率relative index of refractionと呼ぶ。光の場合は，入射側の媒質Iが真空である場合の相対屈折率をとくに絶対屈折率absolute refractive index，あるいは単に屈折率refractive indexと呼び，通常nで表す。これは真空中の光速度cと物質中の光の速さvとの比n＝c/vであり，相対屈折率は，入射側の媒質Iの屈折率n_Iに対する透過側の媒質IIの屈折率n_IIの比となる。…

※「absolute refractive index」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報