The Systeme International d'Unites (SI) has been adopted and is defined
by IS0 1000.

**Meter**

**(m).**

The meter is the length equal to 1 650 753.73 wavelengths in vacuum of the radiation
corresponding to the transition

between the levels 2p

between the levels 2p

_{10}and 5d_{5}of the krypton-86 atom.**Kilogram**

**(kg).**

The kilogram is the unit of mass; it is equal to the mass of the international
prototype of the kilogram.

**Second**

**(s).**

The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the
ground state of the caesium-133
atom.

**Ampere**

**(A).**

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 m apart in vacuum, would produce between these
conductors a force equal to 2 x 10

^{-7}newtons per metre of length.**Kelvin**

**(K).**

The kelvin, unit of thermodynamic temperature, is
the fraction U273.16 of the thermodynamic temperature of the triple point of
water.

**Candela (cd).**

The candela is the luminous intensity, in the perpendicular
direction, of a surface of 1/600 000 m

^{2}of a black body at the temperature of freezing platinum under a pressure of 101 325 newtons per square metre.**The supplementary base units are defined as follows:**

**Plane angle (radian).**

The angle subtended at the centre of a circle of
radius 1 m by an arc of length 1 m
along the circumference.

**Solid angle (steradian).**

The solid angle subtended at the centre of' a sphere
of radius 1 m by an area of 1 m

^{2}on the surface.**Mole (mol).**

It
is the amount of
substance of a system which contains as many elementary entities as there are
atoms in 0.012 kg of carbon-12. The elementary entities must be specified and can
be atom molecules, ion electrons, other particles or specified groups of such
particles.

**Vineeth**

**About The Author:**

He is a marine engineer sailing with British Petroleum.He has keen interest on compiling marine exam notes.

You can catch him on Google+