Question

define Snell's law and refractive index of a material

Answer 1

the ratio of sine of angle of incidence to the sine of angle of refraction is a constant , for the light of a given colour and for the given pair of media .this is also known as Snell's law

Answer 2

refractive index=this is a ratio of two medium .such that if we find refractive index of medium n with respect of medium m than we can write it as
speed of light in medium n / speed of light in medium m.
Snell law = sine angle i / sine angle r = constant. it is also a refractive index