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Abbe Number

Abbe number is related to the optics, which is a growing branch of physics. The field of optics impacts an ever expanding range of applications in physics, engineering and technology. The parallel emergence of lasers, fiber optics, nonlinear devices, and a variety of semiconductor sources and detectors in the 1960's initiated a continuing period of rapid development in applied and theoretical optics. The need for a variety of updated optics texts with different approaches and emphases is apparent, both for students of optics and for practitioners who need an occasional review of the basics.

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Definition

The Abbe number is nothing but a measure of the dispersion of a material connected to the refractive index of that material. Ernst Abbe (1840-1905), the German physicist found this and it is named after him. The Abbe number of a material is defined as,

$V$ = $\frac{n_{d}-1}{n_{F}-n_{C}}$

Where $n_{d}$, $n_{F}$, $n_{C}$ are the refractive indices of the material at the wavelengths of the $d-,\ F-$ and $C-$ spectral lines (587.6 nm, 486.1 nm and 656.3 nm respectively).

Abbe Value of Lenses

The Abbe value indicates the ability of a lens material to purely refract white light without chromatic aberration. It is sometimes referred to as the Nu value, and runs between 1 and 100. The closer the Abbe number is to 100, the more efficient the lens  material. A high Abbe number indicates that the material is not likely to cause chromatic problems when viewing objects through portions of the lens other than the optical center. A low Abbe number indicates that the material could cause chromatic distortion problems. The given table describes the lens material and its Abbe number.

Abbe Values of Common Lens Materials

 Material Index Glass, crown 59 CR-39 58 Spectralite 47 High index 1.56 (resin) 39 High index 1.60 (resin) 37 High index 1.66(resin) 32 Polycarbonate 31 High index glass 25

Abbe Prism 