Question

Which of the following can be an emergent ray, when an incident ray strikes the rectangular glass block from air?

Answer 1

Hint:When a light ray passes from one medium to another medium, refraction takes place and the light ray bends either towards or away from the normal depending upon the refractive indices of both the medium. A rarer medium is one with a lesser refractive index and a denser medium is one with a higher refractive index.
-When a light ray passes from a rarer medium to a denser medium, the refracted ray bends towards the normal.
-When a light ray passes from a denser medium to a rarer medium, the refracted ray bends away the normal.

Complete answer:
We know that when a light ray passes from one medium to another medium, it bends either towards or away from the normal depending upon the refractive indices of both the medium.Let us draw the diagram given in the question again.

The refractive index of air is 1 and refractive index of glass is 4. Hence, air is the rarer medium and glass is the denser medium. Let us draw refracted rays for four rays in the question.

In the ray 1, the refracted ray moved towards the normal and when it emerged out, it moved away from the normal. In the ray 2, there is no bending of the light ray even when it passes through different media. This option is also wrong.

In the ray 3, the refracted ray bends away from the normal. When the ray is coming out of the glass block, it is bent towards the normal. This is the exact opposite of what should actually happen. Hence, this option is wrong. In the ray 4, the refracted ray bent away from the normal and the emerged ray bent away from the normal. Since, the refracted ray bent away from the normal, it should actually bend towards the normal, this option is also wrong.

Hence, the right answer is option A.

Note:We need to remember that when a light ray passes from a rarer medium to denser medium, it bends towards the normal. When it passes from denser medium to rarer medium, it bends away from the normal. The relation between the incident and refracted angles can be given by Snell’s Law which is given by:
$\dfrac{{\sin i}}{{\sin r}} = \dfrac{{{\mu _2}}}{{{\mu _1}}}$
Always draw the incident rays, refracted rays, it will make the question simpler and easier to solve.