Refractive Index in terms of Speed of Light
The refractive index of a medium may be defined in terms of the speed of light as follows
Refractive index =
or µ =
Refractive Index in terms of Wavelength
Since the frequency (n) remains unchanged when light passes from one medium to another, therefore,
Relative Refractive Index
The relative refractive index of medium
2 with respect to medium 1 is defined as the ratio of speed of light (v1) in the medium 1 to the speed of light (v2) in medium 2 and is denoted by 1µ2.
Thus, 1µ2 =
As refractive index is the ratio of two similar physical quantities, so it has no unit and dimension.
Factors on which the refractive index of a medium depends are :
(i) Nature of the medium.
(ii) Wavelength of the light used.
(iv) Nature of the surrounding medium.
It may be noted that refractive index is a characteristic of the pair of the media and also depends on the wavelength of light, but is independent of the angle of incidence.