Micrometre

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1 micrometre =
SI units
1.0000×10^−6 m1.00000 μm
US customary / Imperial units
3.2808×10^−6 ft39.370×10^−6 in
 
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1 micrometre =
SI units
1.0000×10^−6 m1.00000 μm
US customary / Imperial units
3.2808×10^−6 ft39.370×10^−6 in

The micrometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: µm) or micrometer (American spelling) is an SI derived unit of length equaling 1×10−6 of a metre (SI standard prefix "micro-" = 10−6); that is, one-millionth of a metre (or one-thousandth of a millimetre, 0.001 mm, or about 0.000039 inch). The symbol µm is sometimes rendered as um if the symbol µ cannot be used.

The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of cells and bacteria.[1]

The symbol for the SI prefix micro-, µ, is a Greek lowercase mu, μ. In Unicode, it has a codepoint distinct from that of the Greek letter lowercase mu so that machines can recognize it as the SI prefix symbol rather than as a letter. Many fonts use the same glyph for the two characters.

SI standardisation[edit]

The term micron representing the micrometre, was officially accepted between 1879 and 1967, but officially revoked by the International System of Units (SI) in 1967.[2]

Nevertheless, in practice, "micron" remains a widely used term in preference to "micrometre" in many English-speaking countries, both in academic science (including geology, biology, physics, and astronomy) and in applied science and industry (including machining, the semiconductor industry, and plastics manufacturing).[citation needed] Additionally, in American English the use of "micron" helps differentiate the unit from the micrometer, a measuring device, because the unit's name in mainstream American spelling is a homograph of the device's name.

See also[edit]

References[edit]

  1. ^ "micrometre" Encyclopædia Britannica Online, accessed 17 March 2012
  2. ^ BIPM - Resolution 7 of the 13th CGPM (1967/68), "Abrogation of earlier decisions (micron, new candle.)"