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### PHYSICS DICTIONARY

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Tangential Stress

When a tangential force is applied on a body such that there is a change in shape of the body only, then the tangential force per unit area is called tangential stress.

Telescope

An arrangement of lenses and mirrors that collects visible light, allowing direct observation or photographic recording of distant objects is called as telescope. A refracting telescope uses lenses to focus light to produce a magnified image. Compound lenses are used to avoid distortions such as spherical and chromatic aberrations. A reflecting telescope uses mirrors to view celestial objects at high levels of magnification. Most large optical telescopes are reflecting telescopes because very large mirrors, which are necessary to maximize amount of light received by telescope, are easier to build than very large lenses.

Temperature of Inversion (Gases)

The temperature of a gas is the temperature below which a gas is cooled in Joule Thomson expansion and above which gas is heated. In other words, the temperature at which sign of Joule Thomson effect gets reversed.

Temperature

Degree of hotness of a body

Temporal Coherence

The coherence with time in the waves from coherent source travelling in one path is called temporal coherence.

Tensile Strain

If there is increase in length of object due to application of longitudinal stress then it is called tensile strain.

Tensile Strength

The maximum stress, in tension, that may be sustained without fracture.

Tensor Analysis

The study of the fact that “the fundamental laws of physics should possess the same form in all coordinate systems” known as invariant formulation of physical laws is embodied in “Tensor analysis”. Tensor analysis is generalization of vector analysis.

Tephigram

It is the name given for temperature-Entropy diagram. It is useful for applications of meteorology, work value of fuel etc.

Terminal Velocity

The maximum velocity which a body attains when its falls through air under gravitational force.

This type of radiation is present in small quantities all around us and is more or less in escapable. The main source of terrestrial radiation is the element uranium and its decay products such as thorium, radium, and radon. Although the overall natural concentration of these radioactive materials is within the tolerable range of humans, some parts of the world have been identified where higher levels of uranium and thorium in surface soil have increased the radiation to dangerous levels. The two isotopes of radon, 222Rn and 220Rn, and their daughter products are the most commonly found hazardous radioactive elements in our surroundings. The main cause of concern with respect to these α-emitting isotopes is their inhalation or digestion, in which case the short range α-particles continue to cause damage to internal organs that can lead to cancer.

Tesla

The SI derived unit of magnetic flux density, equal to the magnitude of magnetic field vector necessary to produce a force of one Newton on a charge of one Coulomb moving perpendicular to direction of magnetic field vector with a velocity of one meter per second. It is equivalent to one Weber per square meter.

Thermal Conductivity (Insulator)

When one part of crystal is heated, a temperature gradient is set up. In the presence of temperature gradient, heat will flow from the hotter to cooler region. The ratio of this heat current density to the magnitude of temperature gradient is called thermal conductivity.

Thermostat

Thermostat is a device used to maintain steady temperature. It is equipped with bimetallic strip.

Theory of Everything

Hypothetical theory aimed at single equation comprising four types of interactions.

Thermal Capacity

The quantity of heat energy required raising the temperature of a given mass of a substance by 1oC or 1oK is called thermal capacity.

Thermal Equilibrium

When the temperature in all parts of system is same as that of surroundings, the system is said to be in thermal equilibrium.

or

Whenever there is no exchange of heat between the bodies, the bodies are said to be in thermal equilibrium.

Thermal Evaporation Method

It is a thin film growing technique. The principle involves heating the substance more than its melting point in order to produce vapors of it to get deposited on substrate.