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
Rockwell
Hardness Tests
They are tests
for measurement of hardness. A hardness
number is determined by the difference in depth of penetration resulting from
the application of an initial minor load followed by a larger major load.
Roentgen
Equivalent Man (REM)
The dose
equivalent is measured in units of REM when the dose is in RADs.
Roentgen
It is defined as
the exposure resulting in an ionizing charge of 1esu in 1 cm3 of air at 0 oC
and 760mm of Hg pressure (corresponding to a mass of 0.001293gms). One roentgen
equals 2.58 x 10-4 C/Kg.
Rolling
Friction
When one body
rolls over another body, the friction that acts between those bodies is rolling
friction.
Rotating
Crystal Method
A method used to
study crystal structure. In this method a monochromatic beam of X-ray is
incident on a rotating single crystal sample. Diffraction maxima occur when the
sample orientation relative to the incident beam satisfies Bragg’s law.
Rotation
It is type of
motion of body, in which every particle of body describes circular path and
moves along concentric circles about the centre of the rotation. Every particle
of the body experiences the same angular displacement, angular velocity and
angular acceleration as any other particle of the body.
Rotational
Spectrum
Rotational spectroscopy is concerned with the measurement of the
energies of transitions between quantized rotational states of molecules in
the gas phase. Rotational
spectroscopy has primarily been used to investigate fundamental aspects of
molecular physics. It is a uniquely precise tool for the determination of
molecular structure in gas phase molecules.
Rotatory
Motion
Motion
of a body is said to be rotatory under following conditions:
i)
Every
particle of the body describes circular path and they move along concentric
circles about centre of rotation.
ii) Every
particle of body experiences the same angular displacement, angular velocity
and angular acceleration as any other particle of the body.
iii) It can be produced or changed by an
unbalanced torque.
Roughing
Pump
Pump which
exhausts to atmosphere. This type of pump is usually meant to create low vacuum
in the closed vessel.
Rutherford
It is a unit of Radioactivity. 1Roentgen =
106 disintegrations/sec.
Rutherford
Scattering
Rutherford
scattering, first discovered by Lord Rutherford, refers to the elastic scattering
of a heavy charged particle (such as an α-particle) from a nucleus. In his
famous scattering experiment, Rutherford bombarded a thin gold foil by
α-particles and studied how many of them deflected from their original
direction of motion. He noticed that most of the α-particles passed through the
foil un-deflected while very few deflected at very large angles. This
experiment proved that most of the space in the atom is empty and the positive
charge is concentrated into a small space, which we now call nucleus. This
pioneering work by Rutherford changed the way the atoms are visualized forever.
Rutherford scattering is sometimes referred to as Coulomb scattering since the Coulomb
force between the incident particle and the target nucleus is responsible for the
interaction.
Rydberg
Constant
The Rydberg constant, symbol R∞ or RH, named after the Swedish Physicist Johannes Rydberg, is a physical constant relating to atomic spectra in the science of spectroscopy. The value is given by 1.0973731534 x 107 m-1.
