Unit of length: meter. The meter is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second.
Unit of mass: kilogram. The kilogram is the unit of mass of the international prototype of the kilogram.
Unit of electric current: ampere. The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10-7 newton per meter of length.
Unit of time: second The second is the duration of 9,192,631,770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the Celsius-133 atom.
Unit of thermodynamic temperature: kelvin. The kelvin, unit of thermodynamic, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
Unit of amount of substance: mole
- The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is "mol."
- When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
Unit of luminous intensity: candela. The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
Derived Unit: radian The radian is the plane angle between two radii of a circle that cut off on the circumference an arc equal in length to the radius.
Derived Unit: steradian The steradian is the solid angle that, having its vertex in the center of a sphere, cuts off an area of the surface of the sphere equal to that of a square with sides of length equal to the radius of the sphere. |
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