Laws of refraction of light :
(i) First law. The incident ray, the refracted ray and the normal at the point of incidence, all lie in the same plane.
(ii) Second law . The ratio of since of angle of incidence to the since of angle of refraction is constant for a given pair of media. The second law of refractoni is called Snell's law.
Mathematically, it can be written as :
`(sini)/(sinr ) = "Constant" `
Absolute refractive index of a medium . When light foes from vaccum to another medium, then the value of refractive index is called absolute refractive index. It is defined as the ratio of speed of light in veccum or air to the speed of the lightin the medium.
Absolute refractive index `(n) = ("Speed of light in vaccum")/("Speed of light in medium")`
