
Spectral bands are regions of a given
spectrum
A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...
, having a specific range of wavelengths or frequencies. Most often, it refers to
electromagnetic bands, regions of the
electromagnetic spectrum
The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high ...
.
More generally, spectral bands may also be means in the spectra of other types of signals, e.g.,
noise spectrum.
A frequency band is an
interval in the
frequency domain, limited by a lower frequency and an upper frequency. For example, it may refer to a ''
radio band'', such as wireless communication standards set by the
International Telecommunication Union
The International Telecommunication Union (ITU)In the other common languages of the ITU:
*
* is a list of specialized agencies of the United Nations, specialized agency of the United Nations responsible for many matters related to information ...
.
In nuclear physics
In nuclear physics, spectral bands refer to the
electromagnetic emission of polyatomic systems, including condensed materials, large molecules, etc. Each ''
spectral line'' corresponds to the difference in two energy levels of an atom. In molecules, these levels can split. When the number of atoms is large, one gets a continuum of energy levels, the so-called ''spectral bands''. They are often labeled in the same way as the monatomic lines.
The bands may overlap. In general, the energy spectrum can be given by a density function, describing the number of energy levels of the quantum system for a given interval. Spectral bands have constant density, and when the bands overlap, the corresponding densities are added.
''Band spectra'' is the name given to a group of lines that are closely spaced and arranged in a regular sequence that appears to be a band. It is a colored band, separated by dark spaces on the two sides and arranged in a regular sequence. In one band, there are various sharp and wider color lines, that are closer on one side and wider on other. The intensity in each band falls off from definite limits and indistinct on the other side. In complete band spectra, there is a number lines in a band.
This spectra is produced when the emitting substance is in the molecular state. Therefore, they are also called ''
molecular spectra''. It is emitted by a molecule in
vacuum tube
A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
, C-arc core with metallic salt. The band spectrum is the combination of many different
spectral lines, resulting from
molecular vibrational, rotational, and
electronic transition.
Spectroscopy
Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum.
Spectro ...
studies spectral bands for
astronomy
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
and other purposes.
Other applications
Many systems are characterized by the spectral band to which they respond. For example:
* Musical instruments produce different ranges of
notes within the
hearing range.
* The
electromagnetic spectrum
The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high ...
can be divided into many different ranges such as visible
light
Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...
,
infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
or
ultraviolet
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
radiation,
radio
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...
waves,
X-ray
An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
s and so on, and each of these ranges can in turn be divided into smaller ranges.
* A radio communications signal must occupy a range of frequencies carrying most of its energy, called its
bandwidth. A frequency band may represent one
communication channel
A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for infor ...
or be subdivided into many. Allocation of radio frequency ranges to different uses is a major function of radio
spectrum allocation.
See also
References
{{Reflist
Electromagnetic spectrum
Spectroscopy
Spectrum (physical sciences)