**Quality
Factor (Radiation)**

It is a
dimensionless variable weighing factor to be applied to the absorbed dose to
provide an estimate of relative human hazard of different types and energies of
ionizing radiations. Values of quality factor are selected from experimental
values of relative biological effectiveness (RBE), which is ratio of X-ray or
Gamma ray dose to that of radiation in question giving same kind and degree of
biological effect.

**Quality
Factor (Sound) **

** **Physical quantity used to determine
sharpness of resonance which refers to fall in amplitude with change in
frequency on each side of maximum amplitude.

**Quanta**

Concept introduced by Planck to attribute
particle nature to radiation /light. Quanta/quantum describes basic unit of
energy.

**Quantum
Chromodynamics**

The
theory of quantum chromodynamics was developed through the 1950s and 1960s,
resulting in a 1969 Nobel Prize in Physics for Murray Gell-Mann (although
asymptotic freedom was discovered later by David Politzer, Frank Wilczek, and
David Gross, who split the 2004 Nobel Prize in Physics for this work). Experimental
research since then has strongly confirmed the theory, and the six flavors of
quarks predicted by the theory have all been observed experimentally in
laboratory settings.

The
name quantum chromodynamics comes from the naming convention that the quarks
have a "color," which acts sort of like a "charge" in
electrodynamics (but has nothing to do, except in name, with visible colors).
"Chromo" is Greek for "color," so the name comes from the
way these "colors" interact with each other. Quantum chromodynamics
is the theory that describes the strong nuclear interaction, one of the fundamental forces of physics. The theory of quantum chromodynamics explains the
interactions of quarks and gluons, which together make
up hadrons, such
as protons, neutrons, and
mesons.

**Quantum
Electro Dynamics (QED)**

The relativistic theory
of electromagnetic interactions based on picture and exchange of photons is
called quantum electro dynamics.

**Quantum
Mechanics**

Quantum
Physics is a branch of science that deals with discrete, indivisible units of
energy called quanta as described by the Quantum Theory. The quantum mechanics
is concerned with explanation of behavior of physical systems at microscopic
level. The main ideas of quantum mechanics are:

i)
Energy
is not continuous, but comes in small but discrete units.

ii)
Elementary
particles behave both like particles and like waves.

iii) The movement of these particles is
inherently random.

iv) It is physically impossible to
know both the position and the momentum of a particle at the same time. The
more precisely one is known, the less precise the measurement of the other is.

**Quantum
Numbers**

** **They are set of four numbers, the values of
which are used to label possible electron states. Three of the quantum numbers
are integers, which also specify the size, shape, and special orientation of an
electrons probability density; the fourth number designates spin
orientation.

**Quantum
Physics **

"Quantum"
comes from the Latin meaning "how much." It refers to the discrete
units of matter and energy that are predicted by and observed in quantum
physics. Even space and time, which appear to be extremely continuous, have
smallest possible values. Quantum physics is the study of the behavior of matter and energy at
the molecular, atomic, nuclear, and even smaller microscopic levels. There are five main ideas represented in Quantum Theory:

i) Energy is not continuous, but comes in small but
discrete units.

ii) The elementary particles behave both like
particles and like waves.

iii) The movement of these particles is inherently
random.

iv) It is physically impossible to know both
the position and the momentum of a particle at the same time. The more
precisely one is known, the less precise the measurement of the other is.

v) The atomic world is nothing like the
world we live in.

**Quark**

A quark is an elementary particle and a
fundamental constituent of matter. Quarks combine to form composite particles
called hadrons, the most stable of which are protons and neutrons, the
components of atomic nuclei. In the present standard model, there are six
"flavors" of quarks. They can successfully account for all
known mesons and
baryons. The most familiar baryons are the proton and neutron,
which are each constructed from up and down quarks.

**Quarter
Wave Plate **

** **Plate of uniaxial double refracting
crystals, with optic axis parallel to their refracting surface is called as
quarter wave plate. The thickness of quarter wave plate is such that it
produces a path difference of X/Y** **or
a phase difference of π/2 in between ordinary and extraordinary waves.

**Quenching**

Process of adding
suitable gases in small quantities to principal gas in counters to negate the
effects of positive ions induced Geiger discharges, by method of charge
transfer collisions between ions and quench gas molecular.

**Quotient
Law **

Law in tensor
analysis as per which “an entity whose inner product with an arbitrary tensor
(contravariant or covariant) is a tensor, is itself a tensor.