Femto-


This article describes the SI prefix. For the manga character, see Berserk (manga).
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Femto- (symbol f) is a prefix in the metric system denoting a factor of 10−15 or 0.000000000000001. Adopted by the 11th Conférence Générale des Poids et Mesures,[1] it was added in 1964 to the SI.[2] It is derived from the Danish word femten, meaning "fifteen".

Example of use:

  • a proton has a diameter of about 1.6 to 1.7 femtometres.

The femtometre shares the unit symbol (fm) with the older non-SI unit fermi, to which it is equivalent. The fermi, named in honour of Enrico Fermi, is often encountered in nuclear physics.

SI prefixes
Prefix Symbol 1000m 10n Decimal Short scale Long scale Since[1]
yotta Y 10008 1024 1000000000000000000000000 Septillion Quadrillion 1991
zetta Z 10007 1021 1000000000000000000000 Sextillion Trilliard 1991
exa E 10006 1018 1000000000000000000 Quintillion Trillion 1975
peta P 10005 1015 1000000000000000 Quadrillion Billiard 1975
tera T 10004 1012 1000000000000 Trillion Billion 1960
giga G 10003 109 1000000000 Billion Milliard 1960
mega M 10002 106 1000000 Million 1960
kilo k 10001 103 1000 Thousand 1795
hecto h 10002⁄3 102 100 Hundred 1795
deca da 10001⁄3 101 10 Ten 1795
10000 100 1 One
deci d 1000−1⁄3 10−1 0.1 Tenth 1795
centi c 1000−2⁄3 10−2 0.01 Hundredth 1795
milli m 1000−1 10−3 0.001 Thousandth 1795
micro µ 1000−2 10−6 0.000001 Millionth 1960[2]
nano n 1000−3 10−9 0.000000001 Billionth Milliardth 1960
pico p 1000−4 10−12 0.000000000001 Trillionth Billionth 1960
femto f 1000−5 10−15 0.000000000000001 Quadrillionth Billiardth 1964
atto a 1000−6 10−18 0.000000000000000001 Quintillionth Trillionth 1964
zepto z 1000−7 10−21 0.000000000000000000001 Sextillionth Trilliardth 1991
yocto y 1000−8 10−24 0.000000000000000000000001 Septillionth Quadrillionth 1991
  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.

References

  1. ^ International Bureau of Weights and Measures (2006), The International System of Units (SI) (8th ed.), ISBN 92-822-2213-6, http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf 
  2. ^ BIPM - Resolution 8 of the 12th CGPM

External links

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