Fraunhofer lines


Fraunhofer lines

In physics and optics, the Fraunhofer lines are a set of spectral lines named for the German physicist Joseph von Fraunhofer (17871826). The lines were originally observed as dark features (absorption lines) in the optical spectrum of the Sun.

The English chemist William Hyde Wollaston was in 1802 the first person to note the appearance of a number of dark features in the solar spectrum. In 1814, Fraunhofer independently rediscovered the lines and began a systematic study and careful measurement of the wavelength of these features. In all, he mapped over 570 lines, and designated the principal features with the letters A through K, and weaker lines with other letters [Citation
last = Jenkins | first = Francis A.
last2 = White | first2 = Harvey E.
title = Fundamentals of Optics
edition = 4th
publisher = McGraw-Hill
date = 1981
page = 18
isbn = 0072561912
] . Modern observations of sunlight can detect many thousands of lines.

It was later discovered by Kirchhoff and Bunsen that each chemical element was associated with a set of spectral lines, and deduced that the dark lines in the solar spectrum were caused by absorption by those elements in the upper layers of the sun. Some of the observed features are also caused by absorption in oxygen molecules in the Earth's atmosphere.

The major Fraunhofer lines, and the elements they are associated with, are shown in the following table:

The Fraunhofer C, F, G', and h lines correspond to the alpha, beta, gamma and delta lines of the Balmer series of emission lines of the hydrogen atom. The D1 and D2 lines form the well-known "sodium doublet", the centre wavelength of which (589.29 nm) is given the designation letter "D".

Note that there is disagreement in the literature for some line designations; e.g., the Fraunhofer d-line may refer to the cyan iron line at 466.814 nm, or alternatively to the yellow helium line (also labeled D3) at 587.5618 nm. Similarly, there is ambiguity with reference to the e-line, since it can refer to the spectral lines of both iron (Fe) and mercury (Hg). In order to resolve ambiguities that arise in usage, ambiguous Fraunhofer line designations are preceded by the element with which they are associated (e.g., Mercury e-line and Helium d-line).

Because of their well defined wavelengths, Fraunhofer lines are often used to characterize the refractive index and dispersion properties of optical materials.

ee also

* Abbe number
* Timeline of solar astronomy
* Balmer series

References


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Look at other dictionaries:

  • Fraunhofer lines — Fraun ho*fer lines prop. n. pl.. (Physics.) The lines of the spectrum; especially and properly, the dark lines of the solar spectrum, so called because first accurately observed and interpreted by Fraunhofer, a German physicist. [1913 Webster] …   The Collaborative International Dictionary of English

  • Fraunhofer lines — [froun′hō΄fər] n. [after Joseph von Fraunhofer (1787 1826), Bavarian optician, who first mapped them accurately] the dark lines visible in the spectrum of the sun or a star …   English World dictionary

  • Fraunhofer lines — Astron. the dark lines of the solar spectrum. [1830 40; named after J. von FRAUNHOFER] * * * In astronomical spectroscopy, dark lines in a star s spectrum caused by selective absorption of its radiation at specific wavelengths by the various… …   Universalium

  • Fraunhofer lines — Fraun·ho·fer lines frau̇n .hōf ər n pl the dark lines in the spectrum of sunlight Fraunhofer Joseph von (1787 1826) German optician and physicist. Fraunhofer was a master theoretical optician as well as an expert maker of glass lenses and… …   Medical dictionary

  • fraunhofer lines — n.pl. the dark lines visible in solar and stellar spectra. Etymology: J. von Fraunhofer, Bavarian physicist d. 1826 * * * ˈfrau̇nˌhōfə(r) noun Usage: usually capitalized F Etymology: after Joseph von Fraunhofer died 1826 Bavarian optician and… …   Useful english dictionary

  • Fraunhofer lines — /ˈfraʊnhoʊfə laɪnz/ (say frownhohfuh luynz) plural noun the dark lines of the solar spectrum. {See Fraunhofer diffraction} …   Australian English dictionary

  • Fraunhofer, Joseph von — • Optician (1787 1826) Catholic Encyclopedia. Kevin Knight. 2006. Fraunhofer, Joseph von     Joseph von Fraunhofer …   Catholic encyclopedia

  • Fraunhofer , Josef von — (1787–1826) German physicist and optician Fraunhofer, whose family was in the optical trade, was born in Straubing (now in Germany); he was apprenticed to an optician in Munich after his parents died. He subsequently moved to the Utzschneider… …   Scientists

  • Fraunhofer, Joseph von — ▪ German physicist born March 6, 1787, Straubing, Bavaria [Germany] died June 7, 1826, Munich  German physicist who first studied the dark lines of the Sun s spectrum, now known as Fraunhofer lines. He also was the first to use extensively the… …   Universalium

  • Fraunhofer'sche Linien — Die Fraunhoferlinien sind dunkle Linien im Spektrum der Sonne. Solche Linien entstehen dadurch, dass Gase in der Photosphäre der sichtbaren Sonnenoberfläche einen Teil des Sonnenlichts absorbieren. Es handelt sich also um Absorptionslinien. Die… …   Deutsch Wikipedia


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