Question

When white light passes through a hollow prism, then
(A) There is no dispersion or deviation
(B) Dispersion but no deviation
(C) Deviation but no dispersion
(D) There are dispersion and deviation both

Answer 1

Hint White light consists of a collection of component colors that has different wavelengths. Dispersion is defined as the splitting up of these component colors of white light. A white light travels in a straight line and a light ray deviates its path only when it changes the medium of propagation.

Complete Step by step solution
Dispersion is defined as the splitting up of white lights into its component colors of different wavelengths. When white light is passed through a glass slab, the light disperses at the first interface and recombines at the second interface, canceling the effect of dispersion. This happens because the two interacting interfaces are parallel to each other. In the case of a glass prism, the effect of the first glass interface which causes it to disperse does not get canceled because the faces in a glass prism are not parallel to each other. So, the outgoing light rays are dispersed light. This happens due to the difference in the refractive index of the glass prism. That is, refraction is what causes dispersion to happen.
In the question, the light passes through a hollow prism, so the refractive index inside the prism is the same as that outside the prism. This means that refraction does not take place and hence there is no splitting up of white light. As there is no refraction, there is no change in the direction of the ray of white light, so there is no deviation of the direction of light rays.

Therefore, option (A) is the correct option.

Note
While answering these types of questions, do not confuse white light with monochromatic light. Monochromatic light is light that has only one single wavelength or frequency. White light consists of a spectrum of colors that has different wavelengths or frequencies.