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
Specific
Gravity
The relative density of a solid or liquid,
usually when measured at a temperature of 20 oC, compared with
maximum density of water (at 4o C) or of a gas to an equal volume of
air or Hydrogen under prescribed conditions of temperature and pressure.
Specific
Gravity of Fluid
It is the ratio of weight of unit volume of
fluid to unit volume of an equal volume of standard fluid, taken as water at 4 oC.
Specific
Heat at Constant Pressure
Amount of heat
required to raise the temperature of 1 mole of gas by 1oC at
constant pressure.
Specific
Heat at Constant Volume
Amount of heat
required to raise the temperature of 1 mole of gas by 1oC at
constant volume.
Specific
Heat
Amount
of heat required to raise the temperature of unit mass of material through one
Kelvin.
C
= Q/ M∆T; Q is heat required to raise temperature of mass M; and ∆T is raise in
temperature.
Specific
Ionization
Specific
ionization is that number of ion pairs produced per centimeter of travel of
charged particle through matter. Specific ionization is dependent on the mass,
charge, energy of the particle, and the electron density of matter. The greater
the mass of a particle, the more interactions it produces in a given distance.
Specific
Latent Heat
The amount of heat required to change the
state of unit mass of a substance without any change in temperature.
Specific
Latent Heat of Fusion
The quantity of
heat necessary to convert unit mass of a solid substance into a liquid at
constant temperature is called specific heat of melting or fusion. It is
measured in JKg-1 in MKS or Calgm-1 in CGS and denoted by
L.
Specific
Latent Heat of Vaporization
The quantity of
heat necessary to evaporate unit mass of a liquid without any change in its
temperature is known as specific heat of vaporization.
Specific
Strength
The ratio of
tensile strength to specific gravity for a material.
Specific
Volume
Specific volume
represents the space occupied by a unit weight of dry air, in ft3/lb,
and is equal to 1/air density.
Spectral
Emissive Power
The amount of
radiant energy emitted in a range of unit wavelength at a wavelength ‘λ’ per second per unit area of a surface is
called spectral emissive power at wavelength ‘λ’ of that surface.
Spectral Energy Density
The radiant
energy enclosed per unit volume in a unit wavelength range for a particular
wavelength is called spectral energy density.
Spectral
Line
An isolated
bright or dark line in a spectrograph produced by emission or absorption of
light of a single wavelength is called as spectral line. A spectral
line is like a fingerprint that can be used to identify the atoms,
elements or molecules present in a star, galaxy or cloud of interstellar gas.
Spectral
Resolution
Ability of optical system to distinguish
spectral lines corresponding to two very close wavelengths of a light source in
its spectrum is called spectral resolution.
Spectral Series Series of lines in the spectrum of light emitted by excited atoms of an element. Each line being related to
the others in the series by a simple numerical equation
and identified with a particular energy level of an atom
of the element.
Spectrometer
The basic
function of a spectrometer is to take in light, break it into its spectral
components, digitize the signal as a function of wavelength, and read it out
and display it through a computer. The first step in this process is to direct
light through a fiber optic cable into the spectrometer through a narrow
aperture known as an entrance slit. The slit splits the light as it enters the
spectrometer. In most spectrometers, the divergent light is then collimated by
a concave mirror and directed onto a grating. The grating then disperses the
spectral components of the light at slightly varying angles, which is then
focused by a second concave mirror and imaged onto the detector. Once the
light is imaged onto the detector the photons are then converted into electrons
which are digitized and readout through a USB (or serial port) to a computer.
The software then interpolates the signal based on the number of pixels in the
detector and the linear dispersion of the diffraction grating to create a
calibration that enables the data to be plotted as a function of wavelength
over the given spectral range.
Spectrophotometer
A spectrophotometer is employed to measure the amount of light that a sample absorbs. The instrument operates by passing a beam of light through a sample and measuring the intensity of light reaching a detector. According to Beer's law, the amount of light absorbed by a medium is proportional to the concentration of the absorbing material. In general, it is an instrument for producing or recording a spectrum and measuring the photometric intensity of each wavelength present.
