A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Ether
The “ether” is a
hypothetically predicted matter to explain the phenomena of light, and to
account for the flow of energy across empty space. The existence of which was
not proved till date experimentally.
Euclidean
Geometry
The study of
plane and solid figures on the basis of axioms and theorems employed by Greek
mathematician Euclid.
Evaporation
Process by which
atoms or molecules of liquid gain sufficient energy and gets converted to
gaseous state. There is no boiling involved.
Even-even
Nucleus
Nucleus having
even no. of neutrons and protons.
Even-odd
Nucleus
Nucleus having
even no. of protons and odd no. of neutrons.
Event
A given point
(x,y,z,t) in space time is called event.
Exa
Prefix in the
metric system denoting 1018 of a given base unit.
Excitation
Energy
Energy required
for exciting electron from lower energy state to particular higher energy
state.
Excitation
Process of
transferring electrons or atoms from lower energy states to higher energy states.
Excited
State
An electron energy
state, not normally occupied to which an electron may be promoted by the
absorption of some type of energy.
Exciton
It is a bound
state of an electron and hole which are attracted to each other by
electrostatic Coulomb force. It is an electrically neutral quasi particle. It is
regarded as an elementary excitation of condensed matter that can transport
energy without transporting net electric charge.
Exoergic
See exothermic.
Exosphere
The outermost
region of earth’s atmosphere, beginning at an altitude of approximately 550 km
to 700 km and merging with interplanetary medium at around 10000 km. The
exosphere consist chiefly Hydrogen and Helium at extremely low densities.
Temperatures in earth’s atmosphere remain constant with altitude, averaging
about 1500 K. The earth’s exosphere contains the Hydrogen, Geo corona and Van
Allen radiation belts.
Exothermic
Process
Chemical reaction
in which there is release of energy in the form of heat, light or sound. These
processes occur spontaneously. They result in high randomness of entropy of the
system. They are denoted by a negative heat flow (heat lost to the
surroundings) and decrease in enthalpy.
Exponential Function
An Exponential Function is a function of the form y = abx, where both a and b are greater than 0 and b is not equal to 1.
Exposure
It is defined by
ICRU (1980), as “the quotient of dQ by dm, where the value of dQ is absolute
value of total charge of the ions of one sign produced in air when all the
electrons liberated by photons in air of mass ‘dm’ are completely stopped in
air (or) In simple terms, it is defined as total electric charge of the ions
generated by the gamma radiation per given mass of air.
External
Work
When the force is
exerted by the system on its surroundings leading to displacement, then the
work done is called external work.
Extinction
It means
attenuation of incident electromagnetic wave due to absorption by medium or
attenuation by medium.
Extraordinary
Ray
One of the two
refracted rays from double refracting crystals which don’t obey laws of
refraction is called as extra ordinary ray.
Extrapolation
Extrapolation is
an estimation of a value based on extending a known sequence of values or facts
beyond the area that is certainly known.
Extrinsic
Semiconductor
The semiconductors
for which the electrical behavior is determined by impurities, which when
present in even minute concentrations, introduce excess electrons or holes.
Extrusion
A forming
technique where by a material is formed by compression through a die or orifice.
Eye
Piece
Combination
of Two lenses used in optical instruments such as microscope or telescope etc.,
to obtain image free from aberrations.
or
It is type of optical lens placed in optical devices near focal point of objective to magnify image. It is so named as it is usually closest to eye of observer using the optical device.
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