Question

Which of the following is Cauchy’s formula?

(a) μ=A+Bλ^2+Cλ^4

(b) μ=A+\(\frac {B}{\lambda^2} + \frac {C}{\lambda^4}\)

(c) μ=A+B+CBλ

(d) μ=A+\(\frac {B}{\lambda}+\frac {C}{\lambda^2}\)

The question was posed to me during an interview.

Question is from Ray Optics topic in division Ray Optics and Optical Instruments of Physics – Class 12

Answer 1

Right answer is (b) μ=A+\(\frac {B}{\lambda^2} + \frac {C}{\lambda^4}\)

For explanation I would say: Cauchy’s dispersion formula is an empirical expression that gives an approximate relation between the refractive index of a medium and the wavelength of the light. Cauchy’s formula is given as:

μ=A+\(\frac {B}{\lambda^2} + \frac {C}{\lambda^4}\)

Where A, B, and C are the arbitrary constants of the medium.