There are two laws of refraction of light. these are :
a) Incident say , refracted ray and normal lie on same plane .
The concept of plane is shown in the image. In terms of x,y and z co-ordinate system , the y-z plane is shown in light sky blue colour.
b) Ratio of sin of angle of incidence and sine of angle of refraction remains constant for a pair of media. i.e.
sin i / sin r = constant (n)
this constant is called refractive index of medium 2 with respect to medium 1.
or we can write
n2 / n 1 = sin i / sin r
Where n 1 is the refractive index of first medium here air. And n2 is the refractive index of second medium here glass.
∴ n2 = n1 x ( sin i / sin r )
If you have any query regarding the laws of refraction then comment below.