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
Beats
When two sounding
bodies of nearly the same frequency and amplitude are sounded together, the
resultant sound consists of alternate maxima and minima. This phenomenon in
which waxing and vaning of sound at regular intervals is heard, is called
beats. The number of beats heard per second is equal to difference in frequency
between two sounding bodies.
Beer’s
law
Beer
Lambert’s law describes how the intensity of light gets changed with medium and
concentration. It states that the amount of intensity, when passing through any
sample decreases exponentially with increase in thickness of sample and
concentration of medium.
The
law states that, amount of light emerging from a sample is diminished by 3
physical phenomenon i) Amount of absorbing material in its path length
(concentration) ii) The distance, the light must travel through sample (optical
path length) iii) Probability that photon of particular wavelength will be
absorbed by material.
Bel
It is unit for
measuring intensity of sound. Whenever intensity of sound increases by a factor
of 10, the increase in intensity is said to be 1 Bel.
Becquerel
It is SI unit for
activity of radioactive nuclide. Radioactive nuclide is said to have an
activity of 1 Becquerel if it decays at rate of one disintegration per second.
Bernoulli’s
Principle
The principle which
states that the total energy per unit volume of an incompressible, non-viscous
fluid in laminar flow is constant at every point.
Beta
Decay
There are two
types of beta decay denoted by β- (electron emission) or β+ (positron
emission). In case of β- decay, an unstable atomic nucleus with
excess of neutrons
may tend to emit a high energetic electron. In this decay, a neutron is converted into
a proton, an electron and an electron-type antineutrino (the antiparticle of
the neutrino). The process is given by n → p + e− + νe. In case of β+ decay,
unstable atomic nuclei with an excess of protons may tend to emit high
energetic positron. In this decay, a proton is converted into a neutron, a
positron and an electron-type neutrino; p → n + e+ + νe. β+
decay can only happen inside nuclei when the absolute value of the binding energy of the daughter nucleus is greater
than that of the mother nucleus, i.e., the daughter nucleus is a lower-energy
state.
Beta
Particle
The high
energetic negatively or positively charged particles emitted during beta decay are
called as beta particle.
Betatron
It is a type of
particle accelerator that uses alternating electric field produced by varying
magnetic field to accelerate beta particle or electrons in circular orbits. It
consists of circular evacuated tube surrounded by electromagnet. Alternating
current in these windings produces varying magnetic field that periodically
reverses in direction. Electron acceleration is controlled by two forces, one
acting in the direction of motion of electrons and other at right angles to
that direction. The force in direction of electron motion is exerted by
electric field produced via induction by strengthening magnetic field with in
circle; this force accelerates electrons. The second perpendicular force arises
as electrons move through magnetic field, and it maintains electrons in
circular orbit with in closed loop.
Biaxial
Crystal
It is a double
refracting crystal, which have two optic axes along which both the refracted
rays have same speed.
Biconcave
Lens
A lens with two
concave surfaces is called as biconcave lens. A collimated beam of light
passing through the lens is diverged.
Biconvex
Lens
It is a lens with
convex sides on both sides. A beam of light passing through lens will get
converged.
Bifocals
Eye glasses with
two distinct optical powers. They are designed with most convex lens for close
viewing in lower half of eye glass and least convex lens for distant viewing in
upper half.
