Question

The emergent ray in a prism bends ______ the normal.
A. Towards
B. Away from
C. Both A and B
D. None of these

Answer 1

Hint: Refractive ray comes out from the prism is called emergent ray. When a ray of light is travelling from one medium to another medium, then a change in direction will happen due to the difference of the speed of light. This change is known as refraction of light. The direction of the light ray depends upon the speed of light in that medium.

Complete step-by-step answer:

Refraction of light happens, when a ray of light travels from one medium to another. Here the mediums are air and glass. The light gets refracted at boundaries of two mediums due to change in its speed. If the light is passing from fast medium to slow medium, then the light ray bends towards the direction of normal to the boundary between two media. If the light is passing from slow to fast medium, then the light ray bends away from the direction of the normal to the boundary between the two media. Light ray moves faster in rarer medium and slowly in denser medium.
Prism is a transparent body and it has three rectangular faces and two triangular faces. When the ray incident on the prism, the light bends towards the normal. Because at that time light rays move from rarer to denser medium. Then light ray after the refraction will incident on the second face. Here the light ray moves from denser to rarer medium. So, it will bend away from the normal. Hence, the emergent ray bends away from the normal.
Therefore, the correct option is B.

Additional information: Willebroad Snell derived the relationship between the angle of incidence and angle of refraction.

\[{{n}_{i}}\sin {{\theta }_{i}}={{n}_{r}}\sin {{\theta }_{r}}\], where \[{{n}_{i}}\] is the refractive index of incident medium , \[{{n}_{r}}\] is the refractive index of refracted medium, \[{{\theta }_{i}}\] is the angle of incidence and \[{{\theta }_{r}}\] is the angle of refraction. Refractive index is a specific value of a material and that determines the speed of the light through the material.

Note: It is very important to learn the direction of the light when it passes through one medium to another. Do not make mistakes with that. Snell’s law of refraction can be used to find either refractive index or refracting angle if other quantities are available.