Question

Which is the emergent ray in the below figure?

Answer 1

Hint: We will first label all the rays in the diagram, and then find out the emergent ray. The ray incident on the surface is called incident ray. The ray inside the prism is called the refracted ray. The ray that comes out of the prism is called the emergent ray. We know that when a light ray passes from one medium to another medium, the refracted ray bends towards the normal or away from the normal depending upon the refractive indices.

Complete answer:
• When a light ray passes from one medium to another medium, the refracted ray bends either towards or away from the normal depending upon the refractive indices.
• Air has a refractive index equal to 1 and glass has a refractive index of 4. Hence, air is the rarer medium and glass is the denser medium.
• Let us check the diagram given in the question and try finding the incident, refracted and emergent rays.

From the above diagram, we can understand that:
- PQ is the incident ray which is incident on the prism.
- QR is the refracted ray which is bent towards the normal since the light ray passes from the rarer medium to the denser medium.
- RS is the emergent ray which is bent away from the normal since the light ray passes from denser medium to rarer medium.

Hence, the emergent ray is RS.

Note:
- 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.