femto-

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This article describes the SI prefix. For the manga character, see Berserk (manga).
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femto- is an SI prefix (symbol f) in the SI system of units denoting a factor of 10−15 or 0.000 000 000 000 001. Adopted in 1964 by the 12th Conférence Générale des Poids et Mesures [1], it comes from the Danish or Norwegian femten (similar to Swedish femton), from the Old Norse fimmtān, meaning fifteen.

Examples of units:

  • One femtosecond = 10−15 s
  • One femtojoule = 10−15 J

Example:

  • a proton has a diameter of about 1.6 to 1.7 femtometre

Note that the femtometre (10−15 of a metre) shares the same unit symbol (fm) with the older non-SI unit fermi, to which it is equivalent. The fermi, in honour of Enrico Fermi is often encountered in nuclear physics that is characteristic of this scale.

SI prefixes
1000m 10n Prefix Symbol Since[1] Short scale Long scale Decimal
10008 1024 yotta- Y 1991 Septillion Quadrillion 1 000 000 000 000 000 000 000 000
10007 1021 zetta- Z 1991 Sextillion Trilliard 1 000 000 000 000 000 000 000
10006 1018 exa- E 1975 Quintillion Trillion 1 000 000 000 000 000 000
10005 1015 peta- P 1975 Quadrillion Billiard 1 000 000 000 000 000
10004 1012 tera- T 1960 Trillion Billion 1 000 000 000 000
10003 109 giga- G 1960 Billion Milliard 1 000 000 000
10002 106 mega- M 1960 Million 1 000 000
10001 103 kilo- k 1795 Thousand 1 000
10002/3 102 hecto- h 1795 Hundred 100
10001/3 101 deca- da 1795 Ten 10
10000 100 (none) (none) NA One 1
1000−1/3 10−1 deci- d 1795 Tenth 0.1
1000−2/3 10−2 centi- c 1795 Hundredth 0.01
1000−1 10−3 milli- m 1795 Thousandth 0.001
1000−2 10−6 micro- µ 1960[2] Millionth 0.000 001
1000−3 10−9 nano- n 1960 Billionth Milliardth 0.000 000 001
1000−4 10−12 pico- p 1960 Trillionth Billionth 0.000 000 000 001
1000−5 10−15 femto- f 1964 Quadrillionth Billiardth 0.000 000 000 000 001
1000−6 10−18 atto- a 1964 Quintillionth Trillionth 0.000 000 000 000 000 001
1000−7 10−21 zepto- z 1991 Sextillionth Trilliardth 0.000 000 000 000 000 000 001
1000−8 10−24 yocto- y 1991 Septillionth Quadrillionth 0.000 000 000 000 000 000 000 001
  1. The metric system was introduced in 1795 with six prefixes. The other dates relate to recognition by a resolution of the CGPM.
  2. The 1948 recognition of the micron by the CGPM was abrogated in 1967.

[edit] References

  1. ^ BIPM - Resolution 8 of the 12th CGPM

[edit] External links