Define refractive index of a medium.

Explanation

(i) The ratio of sine of angle of incidence to the sine of angle of refraction is called refractive index.
`therefore " "_(1)n_(2)=(sin i)/(sin r)`
(ii) The refractive index of the second medium with respect to the first medium is given by the ratio of the magnitude of velocity of light in the first medium to thta in the second medium. It is represented as
`" "_(2)n_(1)=("velocity of light in medium 1 ")/("velocity of light in medium 2 ")`
`therefore " "_(2)n_(1)=(v_(1))/(v_(2))`

Light ray going from medium 1 to medium 2
(iii) The refractive index depends upon the relative speed of propagation of light in different media.
(iv) Refractive index has no unit.