Abbe Number

Abbe number, abbreviated as \(V_d\), a dimensionless number, is the measure of material's dispersion (variation of refractive index versus wavelength) with high values of V indicating dispersion.  It is used to classify glass and other optically transparent materials.     

 

Abbe Number formula

\(\large{ V_d = \frac{ n_d \;-\;1 }{ n_f \;-\; n_c }  }\)

Where:

\(\large{ V_d }\) = Abbe number

\(\large{ n_c }\) = refractive index at the wavelengths of the Fraunhofer C spectral line

\(\large{ n_d }\) = refractive index at the wavelengths of the Fraunhofer D spectral line

\(\large{ n_f }\) = refractive index at the wavelengths of the Fraunhofer F spectral line