I don't understand how the formula works;(adsbygoogle = window.adsbygoogle || []).push({});

v_{D}= n_{D}-1 / n_{F}-n_{C}

given n_{D},n_{F}and n_{C}are the Fraunhofer's line with wavelength of 589.3, 486.13, and 656.27 respectively in nm.

Now my trouble starts here. Since the wavelengths are already given , V_{D}is always a constant. How does the relationship between wavelength and refractive index goes here? Say if I want to measure a random value of refractive index/wavelength of a glass, how do I put the refractive index of my glass into the above equation?

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# Abbe's Number calculation

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