$(a)$ State the laws of refraction.
$(b)$ $A$ ray of light enters from a medium $A$ into a slab made up of a transparent substance $B$ (as shown in the figure). The refractive indices of medium $A$ and $B$ are $2.42$ and $1.65$ respectively. Complete the path of the ray of light until it emerges out of the slab.

(N/A) The two laws of refraction are:
$(i)$ The incident ray,the refracted ray,and the normal to the interface of two transparent media at the point of incidence,all lie in the same plane.
$(ii)$ The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant,for the light of a given colour and for the given pair of media. This law is also known as Snell's law of refraction.
$(b)$ Since the refractive index of medium $A$ $(n_A = 2.42)$ is greater than the refractive index of medium $B$ $(n_B = 1.65)$,the light travels from a denser medium to a rarer medium. Therefore,the refracted ray will bend away from the normal when entering medium $B$. When the ray emerges from the slab back into medium $A$,it will bend towards the normal. The path of the ray is as shown in the figure.