Question

Refractive index of a medium _______ with increases in wavelength of light.

• A. increases
• B. decreases
• C. remains same
• D. cant say

Answer 1

The correct option is B decreases

The refractive index of materials varies with the wavelength (and frequency) of light. This is called dispersion and causes prisms and rainbows to divide white light into its constituent spectral colors. As the refractive index varies with wavelength, so will the refraction angle as light goes from one material to another. In regions of the spectrum where the material does not absorb light, the refractive index tends to decrease with increasing wavelength, and thus increase with frequency. This is called "normal dispersion".