State laws of refraction.

Explanation

i) The incident ray, the refracted ray and the normal to the interface at the point of incidence lie in the same plane.
ii) The ratio of sine of angle of incidence (i) to the sine of angle of refraction (r) is constant.
`i.e.,(sin i)/(sin r)= "constant"" "........(i)`
This constant is equal to refractive index of second medium with respect to first medium `(n_(12))`.
`implies (sin i)/(sin r)=n_(21)`. This law is called Snell.s law.
When the ray travels from rarer to denser medium, it bends towards the normal and when the ray travels from denser to rarer, medium, the ray bends away from the normal.