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
Fermi
Level
It determines
probability of occupancy of allowed energy states.
Fermi
It is unit of
wave length used in nuclear physics which is named after Italian physicist
Enrico Fermi. One Fermi is equal to one Femto meter i.e. 10-15
meter.
Fermions
Elementary particles
which obey Fermi Dirac statistics having spin ½. They fall in two main classes
according to whether they are lighter than mesons or heavier. The two classes
are Leptons or Baryons respectively.
Ferrite
Ceramic oxide
materials composed of both divalent and trivalent cations.
Ferromagnetism
In some materials
(e.g., Fe, Ni, Co) the non – zero atomic magnetic dipoles interact with one
another and spontaneously produce magnetization over small domains of sizes of few
microns. The different domains may have random orientations resulting in zero
bulk magnetic moment. Macroscopic magnetization arises when the domains are
made to align themselves in a common direction. In ferromagnetic materials for
each value of magnetization, there is no unique value of the field B; it
depends on the history by which the magnetization is reached. This is the
phenomenon of hysteresis.
Ferroelectricity
Phenomenon
exhibited by a group of dielectric materials which exhibit spontaneous
polarization i.e. polarization in absence of an electric field. They are
dielectric analogue of ferromagnetic materials. In ferroelectric materials,
permanent electric dipoles exist.
Ferrous
Alloy
A metal alloy for
which iron is the prime constituent.
Fick’s
first Law
The
diffusion flux is proportional to concentration gradient.
J=-D(dc/dx);
the law holds good for steady state diffusion situations. The negative sign
indicates that ‘J’ is positive when movement is down the gradient. ‘D’ is
diffusivity or diffusion coefficient.
Fick’s
Second Law
The time rate of
change of concentration is proportional to second derivative of concentration.
This law is employed in non-steady state diffusion situations.
Fictious
Force (Pseudo force)
It is force which
does not act on object but appears due to acceleration of non inertial frame of
reference.
Field
A property of a point in space describing
the forces that would be exerted on particle, if it was there.
(or)
Any
physical quantity which takes different values at different points in space and
time.
Fine
Structure Constant
The amount of
splitting of main spectral lines of atom is characterized by dimensionless
constant called fine structure constant. The value is nearly equal to 1/137.
Fine
Structure
The splitting of
main spectral lines of an atom in to two or more components each representing
slightly different wavelength is called as fine structure. It is actually
produced when an atom emits light in making the transition from one energy
state to another. The fine structure of main lines arise from the interaction
of orbital motion of an electron with the quantum mechanical spin of that
electron.
Fissile
Nuclei that can
undergo fission when neutron impinges on them are called fissile nuclei.
Fission
Chamber
Fission
chambers use neutron-induced fission to detect neutrons. The chamber is usually
similar in construction to that of an ionization chamber except that the
coating material is highly enriched U-235. The neutrons interact with the
U-235,
causing fission. One of the two fission fragments enters the chamber while the
other fission fragment embeds itself in the chamber wall.
Flint
Glass
An optical glass
developed by George Ravenscroft in 1675. Flint glass is any highly refractive Lead
containing glass used to make lenses & prisms. It has got high dispersion
(low abbe number).
Fluence
The flux
integrated over a period of time is called as integrated flux or fluence.
Mathematically, it is given by Φ=dN/da; where, dN represents the number of
particles passing through the area ‘da’. Since this relation does not
explicitly contain time, it can also be interpreted to represent the number of
particles incident on a surface area ‘da’ at any instant.
Fluid
Pressure
It is normal
force per unit area of surface. Surface may be a body immersed in fluid or any
imaginary surface with in fluid.
Fluid
Substances capable of flowing are fluids.
They don’t have any fixed shape of their own. They take shape of containing
vessel.
