Spectrum meaning

The range of electromagnetic radiation (electromagnetic waves) in our known universe, which includes visible light. The radio spectrum, which includes both licensed and unlicensed frequencies up to 300 GHz has been defined worldwide in three regions: Europe and Northern Asia (Region 1); North and South America (Region 2), and Southern Asia and Australia (Region 3). Some frequency bands are used for the same purpose in all three regions while others differ. See satellite frequency bands and optical bands.Higher FrequenciesFrequencies above 40 GHz have not been licensed, but are expected to be made available in the future as the technology is developed to transmit at these smaller wavelengths (higher frequencies). The spectrum can be viewed in meticulous detail from the Federal Communications Commission (FCC) and National Telecommunications and Information Administration (NTIA) by visiting www.fcc.gov/oet/spectrum and www.ntia.doc.gov/osmhome/osmhome.html. See electromagnetic radiation and wave.Should Airwaves Be Licensed?There is a great deal of controversy over the licensing of frequencies. In Kevin Werbach's very educational white paper, "Radio Revolution," the author says an artificial scarcity has been created because policy makers do not understand the technology. He states that many believe the traditional policy of dividing the airwaves into licensed bands now impedes progress because today's radio technologies allow for much more sharing of the spectrum than ever before. The old notion that radio waves interfere with and cancel each other is a false one. Waves just mix together and become more difficult to differentiate, but modern electronics can, in fact, separate them.To obtain a copy of this insightful report written in 2003, as well as other related articles, visit Werbach's website at www.werbach.com. See smart radio.

Generally referring to frequency spectrum. See electromagnetic spectrum.

Specter, apparition. [from early 17th c.]

A range; a continuous, infinite, one-dimensional set, possibly bounded by extremes.

Specifically, a range of colours representing light (electromagnetic radiation) of contiguous frequencies; hence electromagnetic spectrum, visible spectrum, ultraviolet spectrum, etc. [from later 17th c.]

(chemistry) The pattern of absorption or emission of radiation produced by a substance when subjected to energy (radiation, heat, electricity, etc.).

(mathematics, linear algebra) The set of eigenvalues of a matrix.

(mathematics, functional analysis) Of a bounded linear operator A, the set of scalar values λ such that the operator A"”λI, where I denotes the identity operator, does not have a bounded inverse; intended as a generalisation of the linear algebra sense.