State the laws of refraction of light. Explain the term 'Absolute refractive index of a medium' and write an expression to relate it with the speed of light in vacuum.

State the laws of refraction of light. Explain the term 'Absolute refr

1.	State the laws of refraction of light. Explain the term 'Absolute refractive index of a medium' and write an expression to relate it with the speed of light in vacuum.
Answer» Solution :Law 1 : The incident ray, the refracted ray and the normal at the POINT of incidence, at the interface of the two transparent media, all lie in the same plane. Law 2 : The ratio of SINE of angle of incidence (sin i) to the sine of angle of refraction (sin r) is a constant, for the light of a given colour and for the given pair of media. This true for angle `0 lt i lt 90^(@)`. `(sin i)/(sin r)=` constant `= MU` This constant value `mu` is called the REFRACTIVE index of the medium. Let a ray of light travel from air to a material medium. Let Speed of light in air = c Speed of light in medium = v Refractive index of medium with respect to air `= mu =("speed of light in air")/("speed of light in medium")=(c )/(v)` This is called the Absolute refractive index of medium.