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
Rayleigh’s
Criterion of Resolution
According to this
criterion, two point sources are resolvable by an optical instrument when
central maximum in diffraction pattern of one falls over first minimum in
diffraction pattern of other and vice versa.
Rayleigh’s
Criterion
Lord Rayleigh put
forward a concept for limit of resolution, called Rayleigh’s criterion. According
to Rayleigh’s criterion, two close point objects or the two close spectral
lines of equal intensities are said to be just resolved by an optical
instrument when the principal maxima of diffraction pattern of one coincides
with the first minima of diffraction pattern of the other.
Rayleigh’s
Jeans Law (Thermal Radiation)
The radiation emitted by black body is
proportional to absolute temperature and inversely proportional to fourth power
of wavelength emitted by body.
Rayleigh’s
Scattering
In the Rayleigh
scattering although there is no resultant change in energy state of molecular
system, the system still participates directly in scattering act. This process
causes one photon of incident radiation to be annihilated and a photon of same
energy to be created simultaneously. The intensity of Rayleigh lines is
generally about 10-3 of the
intensity of incident line.
Reactance
It is property of
electrical circuit by which it opposes passage of alternating current through
it.
Reaction
Rate
The reaction
rate, R, is the number of reactions per second per cubic centimeter of
material.
Reactive
Sputtering
Cathodic
sputtering in which chemical reactions are involved is termed as reactive
sputtering.
Reactor
Coolant
Fluid used to
remove heat from reactor core produced by Nuclear Fission and transmit the
energy to turbine system in the form of steam.
Reactor
Period
Reactor period is
defined as that amount of time, normally in seconds, required for neutron flux
(power) to change by a factor of e, or 2.718.
Real
Gas
No known gas obey
ideal gas conditions and hence term real gas has been coined to distinguish
from ideal gas an imaginary concept. Real gas also called Vanderwalls gas as
the molecules are assumed to be attracting each other, for which Vanderwall’s
forces are responsible.
Real
Image
When a beam of
light diverging from a point after reflection (or refraction) actually
converges to a second point, then second point is called the real image of
first point. It can be formed on screen.
Reciprocity
Theorem (Radiation Physics)
Reversing the
positions of a point detector and a point source within an infinite homogeneous
medium does not change the amount of radiation detected.
Reciprocity
Theorem
Network theorem
applicable as per which, current source & voltage are interchangeable. This
theorem is applicable to the electrical circuit which has single emf.
Recrystallization
Dissolve the
existing crystal and subsequently crystallize a substance from the solution, to
form a purified crystal.
Rectifier
Device used to convert
alternating current to direct current.
Rectilinear
Propagation of Light
Light always
travels in straight lines in a homogeneous medium.
Red
Shift
It has been
observed that some distant nebulae are moving away with a velocity greater than
20x103 km/sec and the important spectral lines appear to shift
towards the red end of the spectrum by 200 Ao. This gives the idea
that the universe is expanding.
Reduced
Mass
In physics and
astronomy, value of a hypothetical mass introduced
to simplify the mathematical description of motion in
a vibrating or rotating two-body system.
The equations of motion of two mutually interacting bodies can be reduced to a
single equation describing the motion of one body in a reference frame centered
in the other body. The moving body then behaves as if its mass were the product
of the two masses divided by their sum. That quantity is called the reduced
mass.
Reduction
The addition of
one or more electrons to an atom, ion or molecule is called as reduction.
Reflecting
Power
The ratio of
amount of radiations reflected by the body in a certain time to the amount of
radiations incident on it in the same time is called reflecting power of body.
Reflection
When light radiation passes from one medium into another having different index of refraction, some of the light is scattered at the interface between two media even if both are transparent.
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