Question

The dispersion of white light occurs because the angle of ………… of different colors is different when passing through the glass prism.
(A) Reflection
(B) Refraction
(C) Incidence
(D) None of these

Answer 1

Hint: Different color lights have different wavelengths so the deviation is also different for different colors. White light consists of different colors at different wavelengths so when they strike the refracting surface due to their difference in speed, they have different angles of refraction causing dispersion.

Complete step-by-step solution
White light is composed of lights of different colors or wavelengths. Relation between wavelength of ingoing light beam and refractive index of a given medium is given as:
 \[\mu = a + \dfrac{b}{{{\lambda ^2}}}\]
When white light strikes a prism, all the light colors strike at the same angle of incidence, but they travel through the prism at different speeds. This difference in speed gives rise to different refraction angles which is further the reason for dispersion of white light.

Therefore, the correct answer is angle of refraction, option (B).

Note: This equation is known as the Cauchy equation and it is only valid in the visible spectrum.
The splitting of white light into its constituent colors is called dispersion of light. Angular dispersion is the angular separation between extreme colors that is
 $\theta = {\delta _v} - {\delta _r} = ({\mu _v} - {\mu _r})A$
It depends upon \[\mu \] and A.