Anti Logarithm
If ‘y’ is result of logarithm of a given
number ‘x’ then ‘x’ is antilog of ‘y’.
Anti Matter
Matter
which comprises of antiparticles.
Anti Particle
Every
fundamental particle is presumed to have an antiparticle which has same mass
but opposite charge.
Anti-Node
Position
of particles on a wave which vibrate simple harmonically with maximum amplitude
is called anti node.
Antistokes Lines
The
smaller frequency lines in Raman spectra are called Anti-Stokes lines.
Aphelion
The
point in the orbit of planet, at which it is farthest from sun, is termed as
Aphelion.
Aperture
Word
attributed to small opening in an optical system or arrangement or instrument,
through which light is made to pass for focusing it on to any plane.
Aplanatic Points
See
Aplanatism
Aplanatism
The
property of the surface by virtue of which all rays starting from a particular
point object on its axis, after reflection or refraction at the surface,
converge or appear to diverge from a single point image, is called aplanatism
and the particular object and image points are called aplanatic points while
the surface is said to be aplanatic surface with respect to those two
points.
Apochromat
A
term applied to photographic & microscope objectives indicating highest
degree of color correction.
Apogee
Point
at which a satellite or any object orbiting earth is farthest from center of
earth. At its apogee, object travels slower than at any other point in orbit.
Arc
The arc refers to the set of points on a circle that
lie in the interior of circle. The arc can be any part of circumference.
or
The arc is a closed segment of a differentiable curve
in the 2D plane.
Archimedes Principle
As per this principle when a body is fully or
partially submerged in a fluid, a buoyant force from the surrounding fluid acts
on the body. The force is directed upward and has a magnitude equal to weight
on fluid that has been displaced by body.
Area
It
is mathematical quantity that describes the amount of space extended by two
dimensional surface area in the plane.
Artificial Transmutation
An
artificially induced nuclear reaction caused by the bombardment of a nucleus
with subatomic particles or small nuclei. The phenomenon was first observed and
proposed by Ernest Rutherford.
Asteroids
They
are small, rocky objects revolving around the sun that are too small to be
called planets. They are also called Planetoids.
Astigmatism
Defect
in optical system where rays that propagate in two perpendicular planes have
different foci. It is a vision condition that causes blurred vision either due
to the irregular shape of cornea, the clear front cover of the eye, or
sometimes the curvature of the lens inside the eye. An irregular shaped cornea
or lens prevents light from focusing properly on the retina, the light sensitive
surface at the back of the eye. As a result, vision becomes blurred at any distance.
Astronaut
A
person who is trained to pilot, navigate, or otherwise participate as a crew
member of a space craft is known as Astronaut.
Astronomical Unit (au)
An astronomical unit is approximately mean distance
between Earth and Sun. It is a derived constant and used to indicate distances
with in solar system. Symbol au is recommended by international astronomical
union.
1a.u. = 149,597,870.691 KM
Astronomy
It
is the Branch of science which deals with study of universe comprising
celestial objects such as planets, stars etc. outside earth atmosphere. The
study covers evolution, composition, motion, etc of universe.
Astrophysics
The
branch of astronomy that deals with the physical and chemical processes that
occur in stars, galaxies and interstellar space is called Astrophysics.
Astrophysics deals with structure & evolution of stars, properties of
interstellar space and its interaction with system of stars, and with structure
and dynamics of cluster of stars such as galaxies.
Athermanous
Substances
opaque to the thermal radiation are called athermanous.
Atmosphere
The
mixture of gases surrounding the earth or other celestial body, held in place
by gravity is referred to as atmosphere. It forms five distinct layers at
different heights. The earth’s atmosphere consists in ascending order, the
Troposphere (containing 90% of the atmosphere mass), the Stratosphere, the Mesosphere,
the Thermosphere and Exosphere. Atmosphere is composed primarily of Nitrogen
(78%), Oxygen (21%) and plays major role in water cycle, Nitrogen cycle &
Carbon cycle.
