PHYSICS DICTIONARY

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Corpuscular Theory

The theory, originally proposed by Newton, and revived with the development of the quantum theory that light consists of a stream of particles.

Corrosion

Deteriorative loss of a metal as a resultant of dissolution to environmental reactions.

                                                (or)

Destruction of metal by getting converted into oxide.

Cosmic Background Radiation

The secondary particles in cosmic rays such as muons, pions, neutrinos etc reaching earth, are called as cosmic background radiation.

Cosmic Rays

High energy particles that bombard earth from anywhere beyond its atmosphere are called as cosmic rays. They mainly originate from supernovae. They include

i) Galactic cosmic rays coming from outside solar system, the composition of which is mainly protons, Helium nuclei and heavy ions.

ii) Anomalous cosmic rays are those coming from interstellar space at edge of heliopause.

iii)Solar energetic particles associated with solar flares and other energetic solar events.

Cosmology

Branch of astronomy which deals with general structure, evolution, and characteristics like space, time etc.

Cosmotron

It was first particle accelerator to impart kinetic energy in the range of GeV to particles especially protons. The maximum energy attained by accelerated particle is about 3.3 GeV. The device was at Brookhaven national Laboratory. It was used to observe various Mesons previously seen only in cosmic rays, and to make first discoveries of heavy, unstable particles.   

Cotangent

In a right angled triangle, the cotangent of an angle is “the length of the adjacent side divided by the length of the opposite side”.

Coulomb Force

 See electrostatic force.

Coulomb

It is the SI unit of electric charge.

Coulombs Law

The electric forces exerted on each other by two point charges separated by a distance are proportional to product of magnitude of two charges and inversely proportional to the square of distance of separation. The forces act along the line joining the two charges.

Couple

A pair of equal and unlike parallel forces acting at different points on rigid body is called Couple.

Covalent Bond

Covalent bond is formed by sharing of pairs of valence electrons between “like” atoms. Covalent bonding is also known as homo polar or electron pair bonding

Covariant Equation

An equation which has the same form in all inertial frames of reference; that is, its form is unchanged by Lorentz transformations.

CPT Invariance Law

All physics interactions are invariant under combined operation CPT irrespective of order of operations.

Creep

The time dependent permanent deformation that occurs under stress is called as creep.

Critical Angle

It is the angle of incidence of ray travelling from denser to rarer medium, for which angle of refraction becomes 90 ^oC.

Critical Damping

The minimum amount of viscous damping that results in a displaced system returning to its original position without oscillation.

Critical Magnetic Field

Maximum magnetic field which when applied to a superconductor below transition temperature, the superconducting property is destroyed.

Critical Mass

It is the minimum quantity of fissile material which reduces loss of neutrons escaping through geometric boundaries, thus making the mass capable of sustaining fission chain.

Critical Pressure

The pressure required to liquefy the gas at critical temperature is called critical pressure of gas.

Critical Temperature(Superconductivity)

See transition temperature. 

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Constant Error

When a physical quantity is measured a number of times using the same instrument, if the error is same in all measurements, then it is called as constant error.

Constant Pressure Gas Thermometer

It is a thermometer in which volume occupied by a given mass of gas at constant pressure is used to determine a temperature.

Constant Volume Gas Thermometer

It has a thin walled glass container and manometer. The glass container is full of gas.

Constantan

An alloy of Copper and Nickel, usually 60% Cu and 40% Ni . The alloy has high resistance and low temp coefficient, hence used in resistance wires and thermocouples.

Constrained Motion of a Rotating Body

If some restrictions are imposed on individual particles of system like restriction to change their positions or velocities, the system is called “constrained system”.

Constructive Interference

Interference at the points where the intensity of light is maximum is called as constructive interference.

Continuous Spectrum

It contains all wavelengths from violet to red. It is given by incandescent (red hot) solids and liquids. It is not the characteristic of an atom or molecule but it is emitted by matter bulk. It depends on temperature of source. It is due to thermal excitation.                                                              

Control Rod

Devices having high absorption cross section for neutrons used in nuclear reactor to control the neutron reactivity , influencing availability of neutrons to cause fission thus effecting criticality of reactor.

Convection

Mechanism of heat transfer through fluids like air or water when comes into contact with an object whose temperature is higher than that of fluid. As temperature of fluid in contact with hot body increases, expands & thus becomes less dense and due to buoyant forces it raises and the position is occupied by cooler surrounding fluid and the process continues.

Converging Lens

See convex lens.

Conversion Electron

See internal conversion.

Convex Lens

It is lens that bulges outward and thicker at center. It is an optical device which converge transmitted light to a focus.

Coolant(Reactor)

Coolant is a fluid having high boiling point and high specific heat, used in nuclear reactor to remove the heat liberated during the fission process in fuel bundles.   

Coolidge X-ray Tube

In 1914 William Coolidge, an American physicist, introduced a new X-ray tube design based on a hot cathode which drastically improved the reliability and performance of clinical X-ray tubes.

The hot cathode consists of a filament made of a high melting point metal, typically Tungsten (melting point 3422 ^◦C) or a Tungsten based alloy, heated to a relatively high temperature to serve as source of electrons. The hot cathode emits electrons thermionically. Emitted electrons are accelerated towards target material (anode), from which X-rays are generated.

Cooper Pairs

Cooper showed that an arbitrarily small attraction between electrons in a metal can cause a paired state of electrons to have lower energy than the Fermi energy, which implies that the pair is bound. BCS theory of super conductors took basis of cooper pairs, which are presumed to be formed due to electron– phonon interaction at extremely low temperatures. The coupling is over a range of hundreds of nanometers. They take character of Boson at low temperatures are condense into ground state.

Coordinate Bond

A coordinate bond is a covalent bond between two atoms where one of the atoms provides both electrons that form the bond.

Coordinate Geometry

The use of algebra to study geometric properties; operates on symbols defined in a coordinate system

Coordinates

Coordinates are set of values that show an exact position of a point or object in reference frame.

Co-ordination Number

Number of nearest neighbor atoms for a particular atom at a lattice point is called as coordinate number. In chemistry, it is the number of atoms linked or bonded to a particular atom.  

Coriollis Force

Fictitious force acting on an object in non-inertial frame is known as coriollis force.

Corona Discharge

An electrical discharge characterized by a corona, occurring when one of two conducting surfaces (such as electrodes) of differing voltages has a pointed shape, resulting in a highly concentrated electric field at its tip that ionizes the air (or other gas) around it. Corona discharge can result in power loss in the transmission of electric power, and is used in photocopying machines and air-purification devices. 

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Compound Pendulum

A rigid body with distributed mass able to freely pivot about a horizontal axis, which doesn’t coincide with center of gravity is called compound pendulum.

Compound

It is combination of two or more chemical elements formed by chemical bonding. Chemical elements are held together in a defined spatial arrangement by chemical bonds.

Compressive Strain

When longitudinal stress is applied, if there is decrease in length, it is called compressive strain.

Compton Effect

When a photon of energy ‘hν’ collides with the electron, some of the energy is given to this electron. Due to this energy, the electron gains kinetic energy and hence the scattered photon will have lower energy or lower frequency or longer wavelength than the incident one. The phenomenon is called as Compton Effect.

Compton Scattering

It is type of interaction of gamma rays with free electrons of absorbing material. The electrons binding energy is very less compared to photon energy. The collision is elastic in nature. Part of energy of incident photon is transferred to electron. Another scattered photon of lower energy gets emerged. 

Concave Lens

It is a lens which diverges or spreads light rays travelling parallel to it.

Concentration

The relative content of a particular element or constituent with in an alloy, usually expressed in weight percent or atom percent.

Condensation

Phase change of gaseous vapor into liquid due to reduction of temperature or compression.   

Conductance

The reciprocal of resistance, is measured by ratio of current flowing through a conductor to the difference of potential between its ends.

Conduction Bond

The range of electron energies (electron orbitals) generally outermost orbitals, in which electrons move freely with in atomic lattice of material as delocalized electrons.

Conduction

Mechanism of heat transfer due to vibration amplitudes of molecules and atoms present in solids.

 

Conductivity (Electrical)

 It is inverse of electrical resistivity and thus characteristic of substance.

                                                  or

It is measured by quantity of electricity transferred across unit area, per unit potential gradient per unit time.  Siemens per meter is the unit for this physical quantity.

Conductivity

The proportionality constant between current density and applied electric field is called conductivity. It is measure of capability of conducting an electric current for a material.

Conductor

Substance or object which permits flow of electrons with less resistance is called as conductor.  In terms of crystal structure, they are materials in which there is overlap of conduction and valence bands.

Cone of Friction

A cone in which the resultant force exerted by one flat horizontal surface on another must be located when both surfaces are at rest, as determined by the coefficient of static friction.

Configuration Space

The configuration of the system of N particles moving freely in space may be represented by position of a single point in 3N dimensional space which is called configuration space of the system.

Conical Pendulum

If the bob of a simple pendulum is pulled to a side and whirled to move along a circle in horizontal plane, the string sweeps a cone and this arrangement is called conical pendulum.

Conservation of Angular Momentum

When no external torque acts, then angular momentum of rotating system remains conserved. 

Conservation of Momentum

When no external forces acts on system, its linear momentum is constant.

Conservative Forces

Forces having property in which work done in displacing an object between two points in space is independent of path taken.

Constancy of Speed of Light

Observers in all un-accelerated reference frames measure the speed of light (in vacuum) from any source as same. The constant is 3 x 10⁸ m/sec. Remarkable property is referred to as constancy of speed of light.