Question

What is the value of cauchy's constant for prism and grating?

Answer 1

Cauchy's equation is an empirical relationship between the refractive index and wavelength of light for a particular transparent material. The refractive index "n" of the material of the prism for wavelength λ is given by 

                                         n= A + B / λ²

where A and B are called Cauchy's Constant for the prism. If the refractive indices n₁ and n₂ of any two known wavelengths  λ₁ and  λ₂ are determined by a spectrometer, the Cauchy's constants A and B can be calculated from the above equation.