Question

A deviation in the path of a ray of light can be produced
(A) by a glass prism but not by a rectangular glass slab
(B) by a rectangular glass slab but not by a glass
(C) by a glass prism as well as a rectangular glass slab
(D) neither by a glass prism nor by a rectangular glass slab

Answer 1

Hint: When a ray of light is incident on a surface separating two transparent media, the ray bends at the time of changing the medium. The angle of incidence $i$ and the angle of refraction $r$ follows Snell’s law
$\dfrac{{\sin i}}{{\sin r}} = \dfrac{{{v_1}}}{{{v_2}}} = \dfrac{{{\mu _2}}}{{{\mu _1}}}$
Where ${v_1}$ and ${v_2}$ are the speed of light in media 1 and media 2 respectively, ${\mu _1}$ and ${\mu _2}$ are the refractive indices of media 1 and media 2 respectively.

Complete step by step solution:
We know that whenever light passes from one media to another, this is deviation in the path of light. The amount of deviation depends on the refractive index of the entering medium.
Now the refractive index of air is close to 1 but the refractive index of glass slab is more than that of air. Since there is a difference in the refractive indices therefore there will be deviation in the path of light ray.
Refractive index of glass slab is greater than that of air hence when ray of light coming from air enters the glass slab there will be deviation in path of light towards the normal as velocity of light decreases in glass slab.
Now in case of glass prism, when light enters glass prism there is change in media which leads to change in refractive indices due to which refraction of light occurs. When a ray of light passes through a glass prism, refraction of light occurs both, when it enters the prism as well as when it leaves the prism. Since the refracting surfaces are not parallel, therefore, the emergent ray and incident ray are not parallel to one another.
Hence light is deviated from rectangular glass slab as well as from glass prism.

Option (C) is correct.

Note: When white light is made to pass through a prism, a spectrum of seven colors is formed which shows that white light is a mixture of seven different colors. Prism only acts as a medium for the separation of the seven colors. When light falls on the glass prism, refraction takes place. Since the wavelength of different components of light is different and the frequency is constant, each component gets deviated by a different angle due to the difference in velocity in the glass medium. The red color having the maximum wavelength deviates the least and forms the upper part of the spectrum whereas violet having the least wavelength deviates the most.