PHYSICS DICTIONARY

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Translucency

 It is the property of the substance transmitting light only diffusively; objects viewed through a translucent medium are not clearly distinguishable.

Transmission Electron Microscopy

The image seen with TEM is formed by electron beam that passes through specimen. Details of internal microstructure features are accessible to observation; contrasts in the image are produced by differences in beam scattering or diffraction produced between various elements of microstructure or defect. Since solid materials are highly absorptive to electron beams, a specimen to be examined must be prepared in the form of very thin foil; this ensures transmission through specimen of an appreciable fraction of incident beam. The transmitted beam is projected onto a fluorescent screen or a photographic film so that the image may be viewed. Magnifications approaching      10⁶ times are possible with TEM, which is frequently utilized in study of dislocations.

Transmission

 It is property of a substance to permit the passage of light, with some or none of the incident light being absorbed in process.

Transmitting Power

 The ratio of amount of radiations transmitted by a body in a certain time to amount of radiations incident on it in the same time is called transmitting power.

Transverse Wave Motion

 Type of wave motion in which particles of medium vibrate at right angles to direction of propagation of wave.

Triple Point

The temperature and pressure combination for a substance at which liquid vapor curve, fusion curve and sublimation curve coincide. It is the combination at which substance coexists in solid, liquid and vapor phases.

Triton

Nucleus of Hydrogen-3 (₁H³ ) atom, consists of one proton and two neutrons bound together with a total binding energy of 8.48 Mev. The H-3 atom, a radioactive isotope of hydrogen with a half life ty₂ of 12.32 yrs, is called as Tritium and consists of a nucleus and one electron.

Tropopause

The boundary between the troposphere and the stratosphere is called the "tropopause", located at an altitude of around 5 miles in the winter, to around 8 miles high in the summer, and as high as 11 or 12 miles in the deep tropics. 

Troposphere

The troposphere is the lowest major atmospheric layer, extending from the Earth's surface up to the bottom of the stratosphere. The troposphere is where all of Earth's weather occurs. It contains approximately 80% of the total mass of the atmosphere. The troposphere is characterized by decreasing temperature with height (at an average rate of 3.5 ^oF per thousand feet, or

6.5 ^oC per kilometer).

Trough

The trough of a wave is the point at which particle has maximum amount of negative or downward displacement from the rest position.

Tuning Fork

 Arrangement of U–shaped rod attached to metal stem, used as a source of standard frequency. It is made of an alloy of Nickel and steel.

Tunnel Diode

A tunnel diode is a P-N junction where both P-and N-type regions are degenerately doped. As a result, the Fermi level in the N-type material is above the minimum of the conduction band and the Fermi level in the P-type material is below the maximum of the valence band. The doping concentrations are so high that the width of the space-charge region at the junction is extremely thin, and usually measures less than 10nm. The diode exhibits negative resistance characteristics.

Twin Boundaries

A twin boundary is a special type of grain boundary across which there is a specific mirror lattice symmetry; that is atoms on one side of boundary are located in mirror image positions of atoms on the other side. The region of material between these boundaries is approximately termed as a twin.

Twin Paradox (Relativity)

It is well known hypothetical concept in relativity under time dilation. As per this concept, one of two twins remains at rest and other moves in space ship moving with nearly velocity of light for some duration and come back. Applying theory of relativity, age of twin in space shuttle appears to be high. This leads to paradox.

Type-I Superconductor

Superconductor which exhibits complete Meissner effect for magnetic fields up to a limit is called critical magnetic field.

Type-II Superconductor

This type is discovered by Schubikov. Superconductor which exhibits Meissner effect till a particular magnetic field range, beyond which admits magnetic flux but retains zero resistance till a particular field value (critical field II) beyond which settles to normal state. 

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Thomson Thermo-Electric Effect

It is the designation of the potential gradient along a conductor which accompanies a temperature gradient, the magnitude and direction of potential varies with substance. The coefficient of Thomson effect or specific heat of electricity is expressed as joules per coulomb per degree centigrade.

Thorium Series

 A radioactive decay series which begins with thorium of mass number 232 and ends with non–radioactive isotope of lead of mass number 208.

Thyrsitor

The thyristor is a four-layered, three terminal semiconducting device, with each layer consisting of alternately N-type or P-type material. It has two stable states, and used as an electronic switch.

Time Dilation

One of consequences of theory of relativity which says that “A moving clock always appears to go slow “. “ Every clock appears to go at its fastest rate when it is at rest relative to the observer. Its rate appears to go on slowing by a factor  sqrt[1-v²/c²)] as its velocity ‘v’ relative to observer goes on increasing.  Where ‘v’ is velocity of observers frame relative to reference frame in which clock is placed.

Time Period

Length of time it takes a particle to make one oscillation

or

Time taken by particle in a wave to complete one vibration.

Time

 Time is presence of motion and forces in universe. Time is a real phenomenon which changes continuously. It is measured by comparison to other motions.

Tisza’s Two Fluid Model

 According to this hypothesis, liquid Helium consists of two independent components normal fluid and super fluid. The normal fluid has energy in excess of zero point energy and behaves as an ordinary liquid and possess no unusual properties except that it is liquid at low temps and the super fluid possess only zero point energy, zero entropy, zero viscosity.

Tone

 When a musical instrument produces sound of a single frequency, it is called as tone.

Torque

 The moment of a force; the measure of force’s tendency to produce torsion and rotation about an axis, equal to vector product of radius vector from axis of rotation to the point of application of force and the force vector.

Total Energy Density

Total energy density of radiation at a point is equal to the total radiant energy enclosed per unit volume around that point for all wavelengths.

Total Internal Reflection

When angle of incidence of a ray travelling from denser to rarer medium is greater than the critical angle, no refraction occurs. The incident ray is reflected back in same medium. The phenomenon is called as total internal reflection. 

Toughness

It is measure of ability of a material to absorb energy up to fracture point.

Transducer

 A device which converts energy from one form to another. For instance, a loud speaker is a transducer that transforms electrical signals into sound energy.

Transformer

 It is an AC static device that transfers electric power from one circuit to another. It raises or lowers the voltage in a circuit but with a corresponding decrease or increase in current.

Transient Equilibrium

The parent and daughter radioactive nuclides can also exist in a transient state of equilibrium in which their activities are not equal but differ by a constant fraction. This happens when the half life of the parent is only slightly higher than that of the daughter.

Transistor

Semiconductor device which consists of two PN junctions formed by sandwiching either P-type or N-type semiconductor between a pair of opposite types. The prefix ‘trans’ means signal transfer property of device while ‘istor’ classifies it as solid element in same general family with resistance.

Transistor Biasing

The proper flow of zero signal collector current and the maintenance of proper collector – emitter voltage during the passage of signals is known as transistor biasing.

Transition Temperature (Superconductivity)

The temperature at which resistance of a substance disappears is called as transition temperature.

Translatory Motion

 Motion of object is said to be translatory under following conditions: i) Every particle of the body experiences the same linear displacement, velocity and acceleration as any other particle of body. ii) All particles travel along parallel paths which may be straight or curved. iii) It can be produced or changed by an unbalanced force. 

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Thermal Expansion

Expansion of liquid, solid or gas due to subjection of temperature.

Thermal Neutron

Neutrons whose average kinetic energy is reduced to that of atoms of medium in which they are travelling at a particular temperature are called thermal neutrons.

                                                       or

When a Neutron moving in a medium attains thermal energy of atoms of medium at ambient temperature, then it is said to be thermal neutron.

Thermal Radiation (Thermodynamics)

It is the mechanism of heat transfer through electromagnetic waves. This type of heat transfer can take place even through vacuum.

Thermal Runaway

The self destruction of an unstabilised transistor is known as thermal runaway.

Thermal Shock:

The fracture of a brittle material as a result of stresses that are introduced by a rapid temperature change is called as thermal shock.

Thermal Stress

Residual stress introduced within a body resulting from change in temperature.

Thermalization of Neutrons

Slowing down of neutrons having high energy to energies below 1eV is called thermalization of neutrons.

Thermionic Emission

 It is defined as emission of charge carriers from surface of a solid or over some kind of potential barrier facilitated by supplying thermal energy to the solid. Charge carriers so released from solid are called thermions and science dealing with this phenomenon is called Thermionics.

Thermionic emission is controlled by 3 characteristics of emitter:

a) Its temperature b) Its material composition (work function) and

c) Its surface area.

Thermocouple

 It is a sensor used for measuring temperature. It consists of two dissimilar metals, joined together at one end. When the junction of two metals is heated or cooled, a voltage is produced that can be correlated back to the temperature.

Thermodynamic Potentials

Energy functions which depend on variables P, V, T and S to completely describe thermodynamic system are called thermodynamic potentials. Four main thermodynamic potentials are Internal energy, Helmholtz energy, Enthalpy & Gibbs free energy.

 

Thermodynamic Scale of Temperature

 It is that scale which doesn’t depend on the nature of its working substance or its thermometric property.

Thermodynamics III^rd Law

The heat capacities of all solids tends to zero as the absolute zero of temperature is approached and that the internal energies & entropies of all substances become equal there, approaching their common value asymptotically.

Thermodynamics II^nd Law

 Every chemical or physical or natural process in nature takes place in such a manner that total energy increases or remains constant.

Thermodynamics I^st Law

 When a definite amount of work is done a certain amount of heat is produced & vice versa.

Thermodynamics

It is experimental or empirical science which deals with macroscopic properties of matter. 

Thermometer

 Device used to measure temperature.

Thermoplastic

Materials which soften when heated (and eventually liquefy) and harden when cooled, process that is totally reversible and may be repeated.

Thermos flask

 See deewar flask.

Thermostat

 Device used to maintain steady temperature. It consists of bimetallic strip used to control the connection.

Thevenin’s Theorem

 In a linear network consisting of emf’s and resistances connected between two points ‘A’ and ‘B’ is equivalent to a single effective emf in series with an effective resistance  connected between ‘A’ and ‘B’.

Thin Film

 Films having thickness between 100 A^o to 10000 A^o.

Thompson Scattering

 Elastic scattering process between a free electron and a photon of low energy.

Thomson Model of Atom

 In 1898, Joseph J. Thomson proposed an atomic model in which mass of atom is distributed uniformly over the volume of atom with a radius of order 1A^o and negatively charged electrons are dispersed uniformly with in a continuous spherical distribution of positive charge. The electrons forms rings and each ring can accommodate a certain upper limit in the number of electrons and then other rings begin to form. With this ring structure Thomson could in principle account for periodicity of properties of elements. Thomson’s atomic model is often referred as “Plum Pudding model “.  

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Structure

The arrangement of internal components of matter: electron structure (on a subatomic level), crystal structure (on an atomic level) and microstructure (on a microscopic level).

Sub – Atomic

Term attributed to particles smaller than atom.

Sublimation

Phase change of solid in to gas directly is called sublimation.

Sun

The sun is star at the center of our solar system. It is one of more than 100 billion stars in our galaxy. It has  diameter of  1,390,000 km; mass of  1.989x1030 kg & temperature: 5800 K (surface) & 15,600,000 K (core); The Sun is, at present, about 70%  hydrogen  and 28% helium by mass everything else ("metals") amounts to less than 2%. This changes slowly over time as the Sun converts hydrogen to helium in its core.

Super Cooling

Process of cooling liquid below its phase transition temperature i.e. freezing point without freezing (no phase transition) is called as super cooling.

Super Fluid

Special phase of matter in which, when cooled to temperatures near absolute zero, the molecules exhibit strange quantum effects which make viscosity of fluid zero.

Super Heating

Process of heating liquid above its boiling point without causing vaporization is called as super heating.

Superposition Principle

When two waves interact, the principle of superposition says that the resulting wave function is the sum of the two individual wave functions.

Superconductivity

Materials that behave as normal metals at temperatures greater than critical temperature but exhibits zero dc resistivity below critical temperature i.e. exhibits perfect diamagnetism.          

Superconductor

 They are metals which when cooled below certain temperature called as critical temperature (usually few degrees above absolute zero) suddenly lose all traces of electrical resistance.

Superposition Theorem

In a linear network consisting of emf’s and linear resistances, the current flowing in any element is the phasor sum of currents that would flow in that element by each potential source, all other sources being replaced at that time by their internal resistances.

Supersonic Speed

 Speed that exceeds speed of sound.

Surface Energy:

The total energy involved in the formation of liquid surface is sum of potential energy due to mechanical work done and heat energy absorbed from the surroundings. The total energy per unit surface area is called surface energy.

Surface Tension

Tangential force per unit length acting at right angles on either side of an imaginary line drawn on free liquid surface is called as surface tension.

Surface Waves

 Seismic waves travelling through surface layers are called surface waves.

Surroundings

 All other matter that can interact with the system.

Symmetric Top

 A symmetric body rotating (or spinning) about an axis which is fixed at one point is called symmetric top.

Symmetric Wave Function

A Wave function is said to be symmetric if the interchange of any pair of particles leave the wave function unchanged.

Synchrotron

It is a circular accelerator, in which particles follow a circular orbit of constant radius inside a vacuum chamber in the form of an evacuated circular tube with larger radius. The evacuated chamber is placed into a magnetic field that changes in time to account for the increase in particle mass with energy. There is no need for magnetic field within the whole circular orbit of the beam; instead, a narrow ring of magnets provides the guiding magnetic field. The particles are accelerated by an RF electric field which is produced in a resonant cavity. The particles pass through resonant cavity a large number of times and gain a small amount of kinetic energy during each passage through cavity. Synchrotrons are used for acceleration of protons.

Systematic Errors

All measurements, direct or indirect, are done through some type of measuring device. Since there is no such thing as a perfect device, therefore one should expect some error associated with the measurement. This type of error falls into the category of systematic errors, which refer to the uncertainties in the measurement due to the measurement procedures and devices. Systematic errors are not statistical in nature and therefore cannot be determined by statistical methods. One of the ways to decrease the systematic uncertainty is to properly calibrate the system.

System of Variable Mass

 Any physical system in which mass increases or decreases with time is called as variable mass system.