Question

What is the standard value or approximate value of Cauchy's constant?

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.

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