## Pages

### PHYSICS DICTIONARY

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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 Ekin and the mass of the material dm, that is K= dEkin/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 oC.

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.