fraunhofer s lines

Absorption lines discovered in 1814 by a German physicist named Fraunhofer (1787-1826), comprising the absorption spectrum present in the continuous spectrum of light emitted from the sun created by the effect of gases in the sun s and earth s atmospheres. Since each line is located at a fixed wavelength, the lines are used for reference in regard to the color (wavelength) characteristics of optical glass. The index of refraction of optical glass is measured based on nine wavelengths selected from among Fraunhofer s lines. In lens design, calculations for correcting chromatic aberrations are also based on these wavelengths.