PHYSICS DICTIONARY

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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. 

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Cerenkov Radiation

Electromagnetic radiation emitted when a charged particle passes through a dielectric medium at a speed greater than phase velocity of light in that medium. The charged particles polarize the molecules of that medium, which then turn back rapidly to their ground state emitting radiation in the process.  For instance, speed of light in water is 0.75C. Matter can be accelerated beyond this speed during nuclear reactions and in particle accelerators.

Cermet

A composite material, consisting of a combination of ceramic and metallic materials is called as ceramic. The most common cermets are the cemented carbides, compound of an extremely hard ceramic, bonded together by a ductile metal such as Cobalt or Nickel. 

CGS Units

Acronym for Centimeter – Gram – Second system is a metric system of physical units based on centimeter as unit of length, gram as a unit of mass, and second as a unit of time.

Chain Reaction

Process of multiplicity of neutrons in nuclear reactor to sustain nuclear fission is called as chain reaction. It was proposed by Leo Szilard in 1933.

Chandrasekhar Limit

It was proposed by Chandrasekhar that no white dwarf star can have mass larger than 1.4 times mass of sun.

Characteristic X-ray Radiation

The production of "characteristic" X-rays by electron bombardment of pure elements was first observed in 1909 by Charles G. Barkla and C.A. Sadler. When heavy metals are bombarded with energetic particles, electrons may get knocked out. If the electrons are knocked out from the inner shells of atom, the vacancy is filled by the transition of electrons from outer shells. This will result in emission of quantized photons, "characteristic" of the element.

Charge Conjugation

It is defined as interchange of particles and antiparticles. It doesn’t simply mean a change over the opposite electric charge or magnetic moment, but the sign of certain charge quantum numbers also change. 

Charge Coupled Device

It is a light sensitive integrated circuit that stores and displays the data for an image in such a way that each pixel in the image is converted into an electrical charge, the intensity of which is related to color in the color spectrum.

Charge Transfer Device

A charge-transfer device has a metal oxide semiconductor (MOS) structure that is composed of many independent pixels where charge is stored in such a way that the charge pattern corresponds to the irradiation pattern. These devices can be linear or two-dimensional. According to the method used to detect the charge pattern, two types of charge-transfer devices can be distinguished: charge-coupled devices (CCDs) and charge-injection devices (CIDs).

Charge

It is characteristic of an object that expresses the extent to which it has excess or deficiency of electrons. If the object has deficiency of electrons, then it is said to be having negative charge. In fact it is technical term used to indicate that an object has been prepared to participate in electrical forces.

Charles law

At constant pressure, the volume of a given mass of gas is directly proportional to its absolute temperature.

(or)

At constant pressure, volume of a given mass of a gas increases (or decreases) by (1/273)^th part of its volume at 0 ^oC, on increasing (or decreasing) the temperature by 1^oC.

Chemiluminescence

Phenomenon of emission of electromagnetic radiation as light by the release of energy from a chemical reaction is called as chemiluminescence.

Chemisorption

If the adsorbate molecules are bound to the surface of adsorbent by chemical bonds, the adsorption is known as chemical adsorption or chemisorption.

Cherenkov Radiation

When a high energy charged particle with non – zero rest mass, such as an electron, travels faster than speed of light in a medium, then it emits a special kind of radiation called Cherenkov radiation. The wavelength of Cherenkov photons falls in and around visible region of EM spectrum. In fact, first Cherenkov radiation was observed by Pavel Cherenkov in 1934 as blue light coming from a bottle of water undergoing bombardment by particles from a radioactive source.

Chi-square Distribution

It is one of the most widely used probability distribution  in  inferential statistics, e.g., in hypothesis testing or in construction of confidence intervals. The Chi-Square distribution is merely the distribution of the sum of the squares of a set of normally distributed random variables. Its value stems from the fact that the sum of random variables from any distribution can be closely approximated by a normal distribution as the sum includes a greater number of samples. Thus the test is widely applicable for all distributions. 

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Cathodic Sputtering

The deposition of metal film by sputtering from a cathode through glow discharge method was first observed by Groove. The ejection of atoms from cathode surface by impinging  energetic particle ions of noble gases such as Helium, Argon, Neon, Krypton at a reduced pressure under high DC voltage give rise to phenomenon called as sputtering.    

Cation

A positively charged metallic ion.

Cauchy’s Dispersion Formula

An empirical expression giving an approximate relation between the refractive index ‘n’ of a medium and the wavelength  ‘λ’ of light. The empirical formula is n = A + B/ λ² where A & B are constants; ‘n’ is refractive index; ‘λ’ is wave length.

Causality Law

Effect cannot precede Cause. The law states that “The interval between two events is same in all inertial frames of reference”.

Causality

The relation between Cause and Effect; later is consequence of first.

Cavendish Experiment

The experiment performed by British scientist Henry Cavendish in 1797-98 using torsion balance to measure the force of gravity between masses in the laboratory, and is the first experiment to yield accurate values for the gravitational constant.  

Celestial Body

It is natural body outside Earth’s atmosphere. Celestial body refers to a single, cohesive structure that is bound together by gravity or electromagnetism and is associated with position in space. 

Celsius Scale

It was named after Swedish astronomer Anders Celsius, who established it. It is the scale designed by considering temperature difference between reference temperatures of freezing & boiling points of water divided into 100 degrees. The freezing point is taken as 0^oC & boiling point as 100^oC. The Celsius scale is widely known as centigrade scale because it is divided into 100 degrees.

Celsius

It is unit of temperature. On Celsius scale of temperature, the lower fixed point is melting point of pure ice at normal atmospheric pressure. This is called 0 ^oC. The upper fixed point is the boiling point of pure water which is designated as 100 ^oC. The gap between the two fixed points is divided into 100 equal parts or degrees.

Cema

One limitation of Kerma is that it is defined only for uncharged particles, such as photons. For charged particles, another quantity called Cema has been introduced. It is analogous to Kerma in definition and is mathematically written as C= dE_con/dM; where dE_con; ‘V’ is the energy lost by charged particles in a material of mass dM. The SI units of Cema are J/kg or Gray.

Center of Mass Frame

It is any inertial frame in which center of mass remains at rest.

Center of Mass

It is the point at which whole mass of body is supposed to be confined. It may lie inside or outside the body. 

Centi

It is a prefix in the metric system denoting a factor of one hundredth. It is used with meter to express lengths in centimeters, a common unit of length in CGS system.

Central Tendency

The central tendency of a distribution is a number that represents the typical or most representative value in the distribution. Measures of central tendency provide researchers with a way of characterizing a data set with a single value. The most widely used measures of central tendency are the mean, median, and mode.

Central Force

A force whose line of action is always directed toward a fixed point is called central force. The point, toward or from which force acts is called central force.

Centre of Gravity

 It is the point of a body through which its weight acts.

Centrifugal Force

It is the radial force acting outwards on the agency which makes body to move in a circular path.

                                              or

The pseudo force which acts radially outwards on body moving along a circle.

Centripetal Acceleration

The acceleration of object in uniform circular motion, which points towards center, is called as centripetal acceleration.

Centripetal Force

It is the force which acts perpendicular to direction of linear velocity to keep body in a circular motion. This force changes direction of linear velocity but not its magnitude.

Centroid

The name attributed to geometrical center of objects shape.

Ceramic

The term “Ceramic” comes from Greek word “keramikos”, which means “burnt stuff” indicating that desirable properties of these materials are normally achieved through high temperature heat treatment process called firing.

or

A compound of metallic and non-metallic elements, for which the inter-atomic bonding is predominantly ionic.