**Kaon**

Any of three
unstable mesons, one having charge +1 and a mass of 966 electron masses, and
two being electrically neutral, with a mass 974 electron masses. Their
half-life is approximately 10^{-8} seconds, and they decay through
the weak force.

**Kellner’s
Eye Piece**

It consists of
two plano-convex lenses of same focal lengths and separated by a distance equal
to the focal length of either lens.

**Kelvin
Planck Statement**

Conversion of
total heat energy into work is impossible.

**Kelvin**

It is the unit of
thermodynamic temperature; it is the fraction 1/273.16 of the thermodynamic
temperature of triple point of water.

**Kelvin’s
Statement of Second Law of Thermodynamics**

It is impossible
to get a continuous supply of work by cooling a body to a temperature lower
than that of coldest of its surroundings.

**Kelvin’s
Thermodynamic Scale**

The ratio of two
temperatures measured on absolute scale is equal to the ratio of heat absorbed
to the heat rejected by a reversible engine working between these temperatures.

**Kepler’s
First Law**

Every planet
revolves round the sun in an elliptical orbit with the sun at one of its foci.
This law is known as law of orbits.

**Kepler’s
Second Law**

The
radius vector joining a planet to the sun sweeps equal areas in equal intervals
of time.

(or)

The
areal velocity of a planet round the sun is constant. This law is known as “law
of areas”.

**Kepler’s
Third Law**

Square of the
time period of revolution of a planet round the sun is directly proportional to
the cube of mean distance of the planet from the sun.

**Kerma**

Kerma
is an acronym of kinetic energy released in a medium per unit mass. It is
defined as the total kinetic energy of all the charged particles liberated by
uncharged particles per unit mass of the target material. Kerma is generally
measured in the same units that are used for absorbed dose, that is, J/kg or Gray.
Kerma is not independent of the type of the target material and therefore must always
be defined with respect to the medium.

Mathematically,
it is written as the quotient of the charged particle’s kinetic energy E_{kin} and the mass of the material dm, that is K=
dE_{kin}/dm.

or

It
is one of the quantities to describe the interaction of ionizing radiation with
matter. It is defined as expectation value of energy transferred to charged
particles per unit mass at a point of interest, including radiative loss of
energy but excluding energy passed from one charged particle to another.

**Kilo
Calorie**

The amount of
energy required to increase the temperature of one kilogram of water by 1 ^{o}C.

**Kilogram**

The Kilogram is
the usual scientific unit of mass. The standard Kilogram is the mass of a
particular cylinder of Platinum Iridium alloy kept near Paris in France. All
masses that are measured are compared with this.