Question

According to Cauchy ,Refractive index is

• A. Directly proportional to wavelength of light
• B. Directly proportional to the square of wave-length of light
• C. Inversely proportional to wavelength of light
• D. Inversely proportional to the square of wave-length of light

Answer 1

The correct option is D Inversely proportional to the square of wave-length of light

Cauchy's equation states relation between refractive index and wavelength of light.

$\mu \left(\lambda \right)=A+\frac{B}{{\lambda }^2}+\frac{C}{{\lambda }^4}......$

Where, A, B, C are constants. Since, wavelength is a very small number of the order of few hundred nano meter we omit the higher powers of .

Thus,

$\mu \left(\lambda \right)=A+\frac{B}{{\lambda }^2}$

The graph for refractive index versus wavelength of light is as follows: