Angular Momentum

It is the ability of a body by virtue of which it imparts rotatory motion to other bodies. Angular momentum is product of linear momentum and perpendicular distance of direction of linear momentum from center of rotation.

Angular velocity

It is defined as rate of change of angular displacement.

Anisotropy

It is the phenomenon of exhibiting different values of a physical property in different crystallographic directions.

Annealing

It is the process of heat treatment of metal by which microstructure and consequently properties of a material are altered. Annealing is generally heating of metal to specific temperature, for certain duration and then allowed to cool slowly thus softening by re-crystallizing. Cold worked metals usually undergo this for relieving strain.

Anode Rays

Rays of positively charged particles formed inside gas discharge tubes. These rays were discovered by Goldstein in 1886.

Anode

It is the electrode in an electrochemical cell that experiences oxidation, or gives up electron.

Anodizing

It is an electrochemical metal finishing process used for increasing thickness and toughness of the naturally occurring protective oxides on surface of metals. The process is called anodizing, as the part to be chemically treated forms the anode electrode of electric circuit. The process increases non-corrosiveness & non-conductivity. 

Anomalous Dielectric Dispersion

The fall in permittivity of a dielectric material with increasing frequency of external electric field is a phenomenon called anomalous dielectric dispersion. 

Anomalous Expansion of Water

When temperature of water is raised from 0 oC, its volume decreases up to 4 oC and above 4 oC its volume increases. This is called anomalous expansion. It is due to formation of more number of Hydrogen bonds.

Anomalous Zeeman Effect

When spectral lines of an atom split into three or more unequally spaced lines in the presence of magnetic field then the phenomenon is called as anomalous Zeeman effect. This usually happens for the systems where net spin i.e. spin quantum number is not zero.

Antenna

A type of transducer that converts RF fields into alternating current or vice versa. A receiving antenna intercepts RF energy and delivers oscillating electric current to electronic equipment, and the transmitting antenna is fed with electric current to generate RF field. They consist of metallic conductors, electrically connected to transistor or receiver.

Anti Ferromagnetism

Phenomenon of magnetic moment (spin moments) of neighboring atoms or ions aligned in exactly opposite directions.

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.