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
Reflectivity
Represents
fraction of incident light that is reflected at the interface.
Refraction
Light that is
transmitted into the interior of transparent material experiences a decrease in
velocity, and as a result it is bent at the interface. This phenomenon is termed
as refraction.
Refractive
Index
The ratio of
light velocity in a vacuum to its velocity in transmitting medium is called as refractive
index of the medium.
Refractometer
Device
designed by Rayleigh, by which the refractive index of a gas at any pressure
can be determined.
Refrigerant
Liquid
which on evaporation produces cooling.
Refrigerator
law
Spontaneous
process cannot be reversed on its own. No refrigerator will have infinite
coefficient of performance.
Refrigerator
It is a device which absorbs heat from a
sink (cold body) and rejects heat at source (hot body) when some work is done on
it by external source of energy.
Regression
Regression
analysis is perhaps the most widely used technique to draw inferences from
experimental data. The basic idea behind it is to fit a function that closely
represents the trend in the data. The function can then be used to make
predictions about the variables involved.
Relative
Density
See Specific
Gravity
Relative
Emittance
The ratio of
radiant energy emitted by a body (surface) at a temperature to the radiant
energy emitted by the same area of an ideal black body in the same time at same
temperature is called as relative emittance of that body (or surface).
Relative
Error
The ratio of
absolute error to the true value is called as relative error.
Relative
Humidity
There is an upper limit for the amount of
humidity which air can hold at a given temperature, beyond which saturation
occurs. Relative humidity tells you what percentage of this maximum amount of
humidity is present in air.
Relative
humidity, RH, is the ratio of the actual water vapor pressure to the vapor
pressure of saturated air at the same temperature expressed as a percentage.
Relative humidity is a relative measure, because the moisture-holding capacity
of air increases as air is warmed.
Relativistic
Physics
Extends range of
application of physical laws to large velocities ‘V’ of order of speed of light
in vacuum, includes classical laws when V<<C and introduces ‘C’ as universal physical
constant.
Remanence
For a
ferromagnetic or ferrimagnetic material, the magnitude of residual flux density
that remains when a magnetic field is removed.
Residual
Stress
A stress that
persists in a material that is free of external forces or temperature
gradients.
Resilience
Capacity of
material to absorb energy when it is deformed elastically and then upon
unloading, to have this energy recovered is called as resilience.
Resistivity
It is the reciprocal of electrical
conductivity and a measure of a materials resistance to the passage of
electrical current.
Resolving
Limit of Microscope
It
is that minimum distance between two objects kept nearby, the images of which
are just resolved by objective of microscope.
or
The
smallest angle subtended by the two objects at the objective of telescope, when
they are just resolved is called resolving limit of telescope.
Resolving
Power of Grating
It is defined as
capacity to separate diffraction maxima of two wavelengths which are close to
each other.
Resolving
Power of Microscope
It is reciprocal of its resolving limit.
Resolving
Power of Telescope
It is defined as inverse of smallest angle
subtended by the two objects at the objective of telescope.
Resolving
Power (Prism)
The ability to form two separate spectral
lines of two close wavelengths by a prism is called its resolving power.
Resolving Power
Ability of an optical instrument to distinguish the images of two very close objects is called the resolving power of optical instrument.
