Question

explain the phenomenon of refraction by a rectangular glass slab​

Answer 1

Refraction through a rectangular glass slab and principle of reversibility of light:

Consider a rectangular glass slab, as shown in figure. A ray AE is incident on the face PQ at an angle of incidence i. On entering the glass slab, it bends towards normal and travels along EF at an angle of refraction r. The refracted ray EF is incident on face SR at an angle of incidence r’. The emerged ray FD bends away from the normal at an angle of refraction e.

Thus the emergent ray FD is parallel to the incident rays AE, but it has been laterally displaced with respect to the incident ray. There is shift in the path of light on emerging from a refracting medium with parallel faces.

Answer 2

Explanation:

• In figure, EO is incident ray. 00' is refracted ray and O'H is emergent ray.

• The point O and O' lie on surfaces separating two transparent media.

• Draw perpendicular NN' to AB at O and perpendicular MM' to CD at O'.

• The light ray at point O has entered from a rarer medium to a denser medium, that is from air to glass. Means angle of refraction becomes smaller than the angle of incident.

• At O', the light ray has entered from glass to air, that is, from a denser medium to a rarer medium and emergent in air goes away from perpendicular. Means the angle of incident becomes larger than the angle of refraction. This angle of refraction is known as angle of emergent.
• Hence, angle of incident and angle of emergent are equal because at opposite refracting surfaces of slab AB and CD having equal and opposite amount of bendings of ray.

• If the ray of light incident is perpendicularly to slab, the refracted ray does not bend that is angle of incident is zero and hence angle of refraction is also zero.

Hope it's helps you.