Question

A beam of white light passing through a prism is split up into its constituent colours. The light which undergoes least deviation is

• A. violet
• B. yellow
• C. red
• D. green

Answer 1

Answer: (C)

red

We know that the relation between wavelength and refractive index is given by $\mu \left(\lambda \right)=A+\frac{B}{{\lambda }^2}$

Thus, as $\lambda$ increases, the refractive index $\mu$ decreases

We know that in the visible spectrum, the increasing order of wavelengths is given by VIBGYOR.

Least deviation corresponds to minimum refractive index.

The minimum refractive index is for the largest wavelength light i.e., Red Light.

Thus, Red light undergoes minimum deformation.