Babinet’s
Compensator
It is a device
used for producing circular & elliptically polarized light and for their
detection.
Back
EMF
It is the
electromagnetic force in an inductive circuit which acts in such a direction so
as to oppose any change of current in the circuit.
Background
Term generally used
in nuclear physics. The background radiation refers to the energetic particles
reaching earth surface mainly due to cosmic rays comprising neutrons, muons,
neutrinos, gamma etc.
Baking
Process in which
materials meant for vacuum application are subjected to heat condition to
reduce outgassing rate.
Ballistic
Galvanometer
A moving coil
galvanometer, in which coil has high inertia that indicates presence of an
electric charge by single impulse imparted to coil by small instantaneous
current, the quantity of electricity that passes being proportional to
deflection of coil.
Ballistic
Pendulum
A physical
pendulum consisting of a large mass suspended from a rod; when it is stuck by a
projectile, its displacement is used to measure the projection’s velocity.
Ballistics
Science of
mechanics that deals with behavior and effects of projectiles, especially
bullets, rockets etc.
Balmer
Series
The spectrum of
wavelength falling in visible region due to transition of electrons from higher
orbits to second orbit is called Balmer series.
Band
Spectrum
This spectrum is
due to transition of electrons combined with rotatory, translatory and vibration
effects of molecules. Hot gases in molecular state produce band spectrum. It is also called molecular spectra. It
consists of bright bands of different colors over dark background. Each band
consists of closely spaced lines. The spacing between two bands and also width
of the band depends on nature of compound. At very high temperature, the band
spectrum changes to line spectrum as the molecules split in to atoms.
Band Theory
Theory which aims
at classifying materials as conductors, insulators, semiconductors based on the
distribution of electron energy states. In solids, due to proximity of atoms,
each distinct atomic state splits into series of closely packed electron states
called as electron energy band. There are three types of electron band
structures possible at 0 K as per this theory.
Band
Width
Term used in
amplifier. It is the band of frequencies over which the amplification gain
remains constant.
Bar
It is a unit of
pressure.
Barns
Unit used for
nuclear scattering interactions. It is used to represent the measure of
probability of interaction between small particles. The value of one barn is 10-28
m2 and is approximate crossection area of Uranium
nucleus.
Barometer
Instrument
invented by Evangelista Torricelli to measure atmospheric pressure and hence for assisting in forecasting weather.
Bartlett
Force
It is type of
nuclear force in which there is exchange of spin coordinates but not position
coordinates between nucleons.
Baryons
They
are a type of Fermions which are heavier than mesons. They constitute the two nucleons with anti
particles & Hyperons.
or
Fermions
whose mass is at least as great as mass of Proton and which can interact
strongly are called Baryons.
Battery
A battery is an
electrochemical cell which consists of an anode, a cathode and an electrolyte.
It is used to provide a static potential for power or release electrical charge
when needed.
BCC
It is a crystal structure equivalent to two interpenetrating
simple cubic cells. The total number of atoms in unit cell is two. The
coordination number is eight.
Beat
Frequency
Phenomenon which can be heard when two sound waves of
different frequency approach human ear; constructive and destructive
interference leads to alternation of soft and loud sound. "The beat
frequency equals absolute value of the difference in frequency of the two
waves."
