Refraction in a Rectangular Slab

Introduction:
When a light ray passes from one medium to another, it changes its direction. This phenomenon is called refraction. Refraction occurs due to the change in the speed of light as it passes through different mediums.

Explanation:
In the case of a rectangular slab, refraction takes place at two interfaces. Let's understand why.

Interface:
An interface is the boundary between two mediums where the light ray enters or exits. In the case of a rectangular slab, there are two interfaces - one where the light enters the slab, and another where it exits.

Refraction at the First Interface:
When a light ray enters the rectangular slab, it undergoes refraction at the first interface. The amount of refraction depends on the angle of incidence and the refractive indices of the two mediums. The incident ray bends towards the normal if the refractive index of the slab is greater than that of the medium from which the light is coming. After refraction, the light ray travels through the slab.

Refraction at the Second Interface:
After traveling through the slab, the light ray reaches the second interface. At this interface, the light ray exits the slab and enters the medium outside the slab. Again, refraction occurs at this interface. The amount of refraction depends on the angle of incidence and the refractive indices of the two mediums. The refracted ray bends away from the normal if the refractive index of the slab is greater than that of the medium outside the slab. Finally, the refracted ray continues to travel in the second medium.

Conclusion:
In summary, refraction takes place at two interfaces in a rectangular slab - one when the light ray enters the slab, and another when it exits the slab. This refraction is responsible for the bending of the light ray as it passes through the slab.