AskDefine | Define angstrom

Dictionary Definition

angstrom n : a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation [syn: angstrom unit, A]

User Contributed Dictionary

English

Etymology

From the name of the physicist Anders Jonas Ångström.

Noun

  1. A very small unit of length, 10-10 m, approximately the size of an atom, used especially to measure the wavelength of electromagnetic radiation or distances between atoms. Abbreviated Å

Translations

  • Finnish: ångström
  • Hebrew: אנגסטרום
  • Japanese: オングストローム
  • Spanish: angstrom
  • Swedish: ångström

Extensive Definition

An ångström or angstrom (symbol Å) (; Swedish: ) is a non-SI unit of length that is internationally recognized, equal to 0.1 nanometre or 1 metres. It is sometimes used in expressing the sizes of atoms, lengths of chemical bonds and visible-light spectra, and dimensions of parts of integrated circuits. It is commonly applied in structural biology. It is named after Anders Jonas Ångström.
Unicode includes the "angstrom sign" at U+212B (Å). However, the "angstrom sign" is normalized into U+00C5 (Å), and is thereby seen as a (pre-existing) encoding mistake, and it is better to use U+00C5 (Å) directly.

History

The ångström is named after the Swedish physicist Anders Jonas Ångström (1814–1874), one of the founders of spectroscopy who is known also for studies of astrophysics, heat transfer, terrestrial magnetism, and the aurora borealis.
In 1868, Ångström created a spectrum chart of solar radiation that expresses the wavelength of electromagnetic radiation in the electromagnetic spectrum in multiples of one ten-millionth of a millimetre, or 1 metres. This unit of length became known as the Ångström unit, and later simply as the ångström.
The visual sensitivity of a human being is from about 4,000 ångströms (violet) to 7,000 ångströms (dark red) so the use of the ångström as a unit provided a fair amount of discrimination without resort to fractional units. Because of its closeness to the scale of atomic and molecular structures it also became popular in chemistry and crystallography.
Although intended to correspond to 1 metres, for precise spectral analysis the ångström needed to be defined more accurately than the metre which until 1960 was still defined based on the length of a bar of metal held in Paris. In 1907 the International Astronomical Union defined the international ångström by making the wavelength of the red line of cadmium in air equal to 6438.4696 international ångströms, and this definition was endorsed by the International Bureau of Weights and Measures in 1927. From 1927 to 1960, the ångström remained a secondary unit of length for use in spectroscopy, defined separately from the metre, but in 1960, the metre itself was redefined in spectroscopic terms, thus aligning the ångström as a submultiple of the metre.
Since the ångström is now defined as exactly 1 metres, there are therefore 10,000 ångströms in a micrometre (commonly called a micron, abbreviated μm, of which there are 1 million to a metre), and 10 in a nanometre (1 nm = 1 metres).
Today, the use of the ångström as a unit is less popular than it used to be and the nanometre (nm) is often used instead (with the ångström being officially discouraged by both the International Committee for Weights and Measures and the American National Standard for Metric Practice).

References

angstrom in Arabic: أنجستروم
angstrom in Asturian: Ángstrom
angstrom in Bengali: অ্যাংস্ট্রম একক
angstrom in Bosnian: Ångstrom
angstrom in Breton: Angström
angstrom in Bulgarian: Ангстрьом
angstrom in Catalan: Àngstrom
angstrom in Czech: Ångström
angstrom in Danish: Ångstrøm
angstrom in German: Ångström (Einheit)
angstrom in Estonian: Ongström
angstrom in Modern Greek (1453-): Άνγκστρομ
angstrom in Spanish: Ångström
angstrom in Esperanto: Angstromo (unuo)
angstrom in Basque: Angstrom
angstrom in Persian: آنگستروم
angstrom in French: Ångström
angstrom in Friulian: Angstrom
angstrom in Galician: Angstrom
angstrom in Korean: 옹스트롬
angstrom in Croatian: Ångstrom
angstrom in Indonesian: Angstrom
angstrom in Icelandic: Ångström
angstrom in Italian: Ångström
angstrom in Hebrew: אנגסטרום
angstrom in Luxembourgish: Angström (Eenheet)
angstrom in Lithuanian: Angstremas
angstrom in Dutch: Ångström
angstrom in Japanese: オングストローム
angstrom in Norwegian: Ångstrøm
angstrom in Norwegian Nynorsk: Ångström
angstrom in Polish: Angstrem
angstrom in Portuguese: Ångström
angstrom in Quechua: Ångström
angstrom in Russian: Ангстрем
angstrom in Simple English: Angstrom
angstrom in Slovak: Angström
angstrom in Slovenian: Angstrem
angstrom in Serbian: Ангстрем (јединица)
angstrom in Finnish: Ångström
angstrom in Swedish: Ångström
angstrom in Thai: อังสตรอม
angstrom in Vietnamese: Ångström
angstrom in Turkish: Angström
angstrom in Ukrainian: Ангстрем
angstrom in Chinese: 埃格斯特朗 (单位)
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