PHYSICS DICTIONARY

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Colloidal Solution

Colloidal solution is a heterogeneous two phase system. One phase consists of dispersed particles of colloidal range and is called dispersed phase. The other phase comprising the medium in which the colloidal particles are dispersed is called dispersion medium.  

Color

An attribute of things that causes visual sensation which results from light rays reflection, transmission or emission. The visual sensation depends on its wavelength.

Color Center

Insulators that are transparent because of large band gap appear colored some times. This color results from selective absorption of some portion of the visible spectrum by imperfections in crystal. Such imperfections in a crystal which selectively absorbs certain colors in visible spectrum are called color centers. Alkali halide crystals when doped with transition element ions or the ions whose salts are normally colored creates color centers in those crystals.

Coma

The rays of light passing through the marginal zones of a convex lens converge nearer to the lens as compared to the paraxial rays because the local length of the lens is less for the marginal rays and large for paraxial rays. For an object highly off principal axis, the images forced by different zones of convex lens are piled on the top of the other in the direction perpendicular to the principal axis.  This transverse displacement of images due to variation of local length of local zones is known as Coma. 

Combined Inversion (CP)

“Landau” advanced a hypothesis that any physical interaction must be invariant under simultaneous reversal of position coordinates and change over from particles to antiparticles.

Comet

A celestial body containing ice and dust, and has highly eccentric orbit.

Compass

Device used to determine geographical direction usually consisting of a magnetic needle mounted on a pivot itself naturally with the earth’s magnetic field so that it points to earth’s magnetic north or South Pole.

Compensated Neutron Ionization Chamber

By the word “compensated”, we mean compensating the response of neutron detector to gamma rays. Compensated ionization chambers consist of two separate chambers; one chamber is coated with Boron-10 isotope, and one chamber without any coating. The coated chamber is sensitive to both gamma rays and neutrons, while the uncoated chamber is sensitive only to gamma rays. Instead of having two separate ammeters and subtracting the currents, the subtraction of these currents is done electrically and the net output of both detectors is read on a single ammeter. If the polarities are arranged so that the two chambers’ currents oppose one another, the reading obtained from the ammeter indicates the difference between the two currents. One plate of the compensated ion chamber is common to both chambers; one side is coated with boron, while the other side is not. The boron coated chamber is referred to as the working chamber; the uncoated chamber is called the compensating chamber. When exposed to a gamma source, the battery for the working chamber will set up a current flow that deflects the meter in one direction. The compensating chamber battery will set up a current flow that deflects the meter in the opposite direction. If both chambers are identical and both batteries are of the same voltage, the net current flow is exactly zero. Therefore, the compensating chamber cancels the current due to gamma rays.

Compensated Pendulum

A clock pendulum in which the effect of changes of temperature of length of the rod is so counteracted, usually by the opposite expansion of different metals, that the distance of centre of oscillation from centre of suspension remains invariable.

Complex number

If you pair a real number with an imaginary number we get complex number, which can be plotted on two dimensional plane. It is of the form a + ib; where ‘a’ is any whole number and ‘ib’ is imaginary part.

Composite Radionuclide

A composite radio nuclide is the one that contains more than one radioisotope at the same time. Most of the radioactive materials found in nature are composite radio nuclide.

Composition

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

Compound Lens

It is an optical device which is an array of simple lenses on a common axis; for correcting optical aberrations.   

Compound Microscope

 A compound microscope uses two lenses, one with very short focal length to form enlarged image; the second one is a short focal length eye piece to magnify the enlarged image.

Compound Nucleus

It is an unstable nucleus which is formed when energetic particles coalesces with nucleus. The energy brought in by incident particle is shared among degrees of freedom of compound nucleus. When one or more nuclear particles acquire energy that is greater than the average binding energy, then such particles leave the nucleus. The concept was first advanced by  

N. Bohr in 1936.

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Climate

The climate where you live is called regional climate. It is the average weather in a place over more than thirty years. To describe the regional climate of a place, people often tell what the temperatures are like over the seasons, how windy it is, and how much rain or snow falls. The climate of a region depends on many factors including the amount of sunlight it receives, its height above sea level, the shape of the land, and how close it is to oceans. Since the equator receives more sunlight than the poles, climate varies depending on distance from the equator.

Clipping Circuit

Circuit with which the waveform is shaped by removing a portion of applied wave is known as clipping circuit.

Clock

Mechanical / electrical device used for measuring and recording time.

Closed System

System which cannot exchange matter with surroundings but only exchanges energy with surroundings.

Closely Packed Structure

Crystal structures which have high atomic packing fraction. There are two types of closely packed structures i) Hexagonal closely packed   ii) Face centered closely packed.

Cloud Chamber

The first instrument which made possible visual observation of tracks of charged particles in their passage through matter was Wilson’s cloud chamber. The principle of the chamber is that super cooled vapor condenses only on charged particles and if charged particles are not present, they remain in vapor phase. If saturated vapor in a chamber is suddenly subjected to an adiabatic expansion, there will be an increase in volume which produces cooling rendering saturated vapor to a super saturated unstable state. If some ions are present in the chamber then condensation takes place on them. Ions are produced by passage of high energy particles through chamber leading to tracks. 

Cloud

Visible mass of fine water droplets, ice particles suspended in atmosphere at high altitudes above sea level.

Cluster

 Group of galaxies is called as cluster.

Co- axial System of Lenses

A combination of lenses having a common principal axis is called a co- axial system of lenses.

Coaxial Cable

Cables having construction of coaxial geometry in which central conductor is separated from braid by insulator  

Cobalt-60

This is a radioactive element formed by bombarding stable isotope of Cobalt i.e. Co⁵⁹ with neutrons. Cobalt-60 has half life of 5.3 years which decays by emitting beta followed by gamma rays. In 99.87% decays, the gamma rays are emitted with 1.17 MeV and in other cases with 1.33 MeV.

Coefficient of Areal Expansion

The ratio of increase in area per degree rise of temperature to the original area of solid.

Coefficient of Contraction

It is defined as the ratio of the minimum cross-sectional area of a jet of liquid discharging from an orifice to the area of the orifice.

Coefficient of Linear Expansion

The ratio of increase in length per degree rise of temperature to the original length of solid.

Coefficient of Mutual Inductance

When two inductors are coupled, the mutual inductance is proportional to square root of product of two inductances. The coupling coefficient has value between 0 and 1.

Coefficient of Restitution

The coefficient of restitution is a measure of the elasticity in a one-dimensional collision. It could be defined as the ratio of the relative velocity after impact to the relative velocity before the impact of two colliding bodies.

Coefficient of Self Inductance

It is a quantity that relates magnitude of self induced voltage in coil to the rate of change of current in the coil. Its SI unit is Henry.

Coefficient of Static Friction

It is proportionality constant between friction and normal force acting on the object over the surface.

Coefficient of Linear Expansion

The ratio of increase in length per degree rise of temperature to the original length of the solid.

Coefficient of Superficial Expansion

The ratio of increase in area per degree rise of temperature to the original area of the solid.

Coefficient of Volume Expansion

The ratio of increase in volume per degree rise of temperature to the original volume of the solid.

 

Coercive Field or Coercivity

In case of ferromagnetic or ferrimagnetic materials, a critical magnetic field must be applied in direction opposite to original field to reduce the magnetic flux density inside the specimen to zero, which is called coercive field and the phenomenon is called coercivity.

Coherence length

It is defined as the maximum distance up to which the pair of electrons (cooper pair) is correlated to produce superconductivity.

Coherence Source

The source which emits coherent waves with respect to both time & space is called coherent source.

Coherent Scattering

Type of scattering in which photon when interacts with matter excites atom and gets scattered.

Coherent Waves

Two light waves of same frequency having constant phase difference are known as coherent waves.

Cohesion

The force of attraction between molecules of same substance is called as cohesion.

Cohesive Energy of Crystal

Energy of crystal is lower than that of free atoms by an amount equal to the energy required to pull the crystal apart into a set of free atoms. This is called binding energy or cohesive energy.

Cold Neutrons

Neutrons having energy less than thermal neutrons are called as cold neutrons. 

Cold Welding

Welding in which fusion of metal is achieved only by applying pressure and no heat. 

Collimator

Device used for constraining the size and angle of spread of a beam of radiation or particles parallel to the tube axis to traverse required length.

Collision

It is the interaction between the bodies for a small time interval due to which the redistribution of momentum takes place.

Colloid

Particles substantially larger than atoms or ordinary molecules but too small to be visible to naked eye. In other words, any particle having dimension in range 10^-7  To 10^-3  cm. 

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Chi square Test

It is also called goodness of fit test. The test allows testing hypothesis using nominal or ordinal data. It does this by testing whether one set of proportions is higher or lower than you would expect by chance. Chi square summarizes the discrepancy between the observed and expected frequencies.

Choke Coil

An inductance coil used in alternating current circuits to limit the current without dissipation of power is called as choke coil. Choke consists of a pure copper wire wounded on a rectangular soft iron to minimize eddy currents and hysteresis losses. 

Chord

A line segment connecting two points in a circle.

Chromatic Aberration

The type of aberration found in images formed by lenses when the source of light is not monochromatic. Formation of a colored and blurred image of white object by a lens due to dispersion is called chromatic aberration. 

Chromosphere

It is narrow layer above Photosphere. It constitutes gaseous layer. It can’t be seen by naked eye and usually appears as narrow, red ring around sun.

Circle

It is a geometrical plane figure which is locus of all points equidistant from central point.

Circular Motion

It is motion of an object in a circle at a constant speed.

Circular Polarization

Light is said to be circular polarized if two electromagnetic waves are perpendicular to each other having same amplitude and phase difference of 90^o.

Circularly Polarized Light

When two plane polarized light waves superpose with a definite phase difference, the resultant light vector revolves with fixed amplitude in a plane perpendicular to direction of propagation of light. In some special cases, the tip of light vector describes a circle. This light is called circularly polarized light.   

Circumference

Perimeter of circle is called as circumference.

Cladding

Process of covering fuel bundles in nuclear reactors to avoid direct physical contact to the moderator or coolant is called as cladding. The cladding material is transparent to the thermal neutrons and withstands very high temperatures. 

Classical Physics

Classical physics is the branch of physics which depends on Newton’s laws of motion. Classical physics is usually divided into several branches, each of which deals with a group of related phenomena. Mechanics is the study of forces and their effect on matter. Dynamics is the study of change in motion because of force. Hydromechanics is the mechanics of fluids; that is, of liquids and gases. Hydromechanics is also known as fluid mechanics. Statics deals with how force affects bodies in constant motion and moving in a constant direction. Optics is the study of the behavior of light. Thermodynamics is the study of heat, and how heat energy is stored, transmitted, and converted to other forms of energy. Acoustics is the study of sound. The study of electricity and magnetism also forms a branch of classical physics.  

Clausius Clapeyrons Equation

Thermodynamics equation which tells us that the change in melting or boiling point with the change in pressure in terms of latent heat of fusion or latent heat of vaporization. It is expressed as

T(dP/dt)=L /T(V2-V1)    

‘T’ is Constant Temperature;    ‘P’ is Pressure

      ‘L’ is Latent heat at const temperature. V₂ and V₁ are specific volumes of substance before and after change in state without change in temp.

     If V₂ > V₁; Melting point increases with increase in pressure and boiling point increases with increase in pressure.

     If V₂<V₁; Melting point decreases with increase in pressure.

Clausius Mossotti Relation

It is the relation between macroscopic dielectric constant and microscopic polarization.

Clausius Statement of Second Law of Thermodynamics

It is impossible for a self acting machine, to transfer heat continuously from one body to another at high temperature.

Clausius Theorem

The sum of quantities of heat transfer during the isothermal change divided by absolute temperature of isothermal in a reversible cycle is zero.

Cleavage

For most brittle crystalline materials, crack propagation corresponds to the successive and repeated breaking of atomic bonds along specific crystallographic planes. This phenomenon is called as cleavage. 

Clebsch-Gordon Coefficient

The Clebsch-Gordan coefficients are sets of numbers that arise in angular momentum coupling under the laws of quantum mechanics.