electromagnetic spectrum

Information about electromagnetic spectrum

The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. The "electromagnetic spectrum" (usually just spectrum) of an object is the frequency range of electromagnetic radiation with wavelengths from thousands of kilometers down to fractions of the size of an atom. It is commonly said that EM waves beyond these limits are uncommon, although this is not actually true. The short wavelength limit is likely to be the Planck length, and the long wavelength limit is the size of the universe itself (see physical cosmology), though in principle the spectrum is infinite. The waves can range from the size of the earth (radio waves) to as small as a atomic nucleus (gamma ray).

Electromagnetic energy at a particular wavelength λ (in vacuum) has an associated frequency f and photon energy E. Thus, the electromagnetic spectrum may be expressed equally well in terms of any of these three quantities. They are related according to the equations:

wave speed (c) = frequency x wavelength

$\text{[math]}$

and

$\text{[math]}$

where:

c is the speed of light, 299,792,458 m/s (exact).
h is Planck's constant, $\text{[math]}$ .

So, high-frequency electromagnetic waves have a short wavelength and high energy; low-frequency waves have a long wavelength and low energy.

When light waves (and other electromagnetic waves) enter a medium, their wavelength is reduced. Wavelengths of electromagnetic radiation, no matter what medium they are travelling through, are usually quoted in terms of the vacuum wavelength, although this is not always explicitly stated.

Spectra of objects

Electromagnetic Spectrum Image.

Nearly all observable objects in the universe emit, reflect or transmit some light. (One hypothetical exception may be dark matter, which, along with Dark energy make up 96% of the universe's total mass.) The distribution of this light along the electromagnetic spectrum (called the spectrum of the object) is determined by the object's composition. Several types of spectra can be distinguished depending upon the nature of the radiation coming from an object:

If the spectrum is composed primarily of thermal radiation emitted by the object itself, an emission spectrum occurs.
Some bodies emit light more or less according to the blackbody spectrum.
If the spectrum is composed of background light, parts of which the object transmits and parts of which it absorbs, an absorption spectrum occurs.

Electromagnetic spectroscopy is the branch of physics that deals with the characterization of matter by its spectra.

Spectrum of incandescent lamp, in IR range, with b/g noise in yellow

A Halogen incandescent lamp, has a light spectra as shown in the accompanying figure. The figure shows just the infrared end of the whole spectra, which is limited by the resolution of the spectrum analyzer from 600 nm to 1500 nm, in the optical window, typical to fiber optic communication systems.

Wave characteristics

External links

U.S. Frequency Allocation Chart — Covering the range 3 kHz to 300 GHz (from Department of Commerce)
Canadian Table of Frequency Allocations (from Industry Canada)
UK frequency allocation table (from Ofcom, which inherited the Radiocommunications Agency's duties, pdf format)
The Science of Spectroscopy - supported by NASA, includes OpenSpectrum, a Wiki-based learning tool for spectroscopy that anyone can edit

• • [ e] The Electromagnetic Spectrum
Visible (optical) spectrum	(Sorted by wavelength, short to long) Gamma ray • X-ray • Ultraviolet • Visible spectrum • Infrared • Terahertz radiation • Microwave • Radio waves
Microwave spectrum	W band • V band • K band: K_a band, K_u band • X band • C band • S band • L band
Radio spectrum	EHF • SHF • UHF • VHF • HF • MF • LF • VLF • ULF • SLF • ELF
Wavelength designations	Microwave • Shortwave • Mediumwave • Longwave

Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. These components oscillate at right angles to each other and to the direction of propagation, and are in phase with each other.
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1 kilometre =
SI units
0 m 010⁶ mm
US customary / Imperial units
0 ft 0 mi

A kilometre (American spelling: kilometer, symbol km
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atom (Greek ἄτομος or átomos meaning "indivisible") is the smallest particle still characterizing a chemical element.
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The Planck length, denoted by , is the unit of length approximately 1.6 × 10⁻³⁵ metres, 6.3 × 10^-34 inches, or about 10^-20 times the diameter of a proton. It is in the system of units known as Planck units.
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The Universe is defined as the summation of all particles and energy that exist and the space-time in which all events occur. Based on observations of the portion of the Universe that is observable, physicists attempt to describe the whole of space-time, including all matter and
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Physical cosmology, as a branch of astronomy, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. Cosmology involves itself with studying the motions of the celestial bodies and the first cause.
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The word infinity comes from the Latin infinitas or "unboundedness." It refers to several distinct concepts (usually linked to the idea of "without end") which arise in philosophy, mathematics, and theology.
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In physics, wavelength is the distance between repeating units of a propagating wave of a given frequency. It is commonly designated by the Greek letter lambda (λ). Examples of wave-like phenonomena are light, water waves, and sound waves.
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Lambda (uppercase Λ, lowercase λ) is the 11th letter of the Greek alphabet. In the system of Greek numerals it has a value of 30. Letters that arose from Lambda include the Roman L and the Cyrillic letter El (Л, л).
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FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. A sequel, titled Amplitude was released in 2003.
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Photon

Photons emitted in a coherent beam from a laser
Composition: Elementary particle
Family: Boson
Group: Gauge boson
Interaction: Electromagnetic
Theorized: Albert Einstein (1905–17)
Symbol: or
Mass: 0^[1]
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energy (from the Greek ενεργός, energos, "active, working")^[1] is a scalar physical quantity that is a property of objects and systems of objects which is conserved by nature.
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speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning "swiftness".^[1] It is the speed of all electromagnetic radiation, including visible light, in a vacuum.
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Planck constant (denoted ) is a physical constant that is used to describe the sizes of quanta. It plays a central role in the theory of quantum mechanics, and is named after Max Planck, one of the founders of quantum theory.
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In astrophysics and cosmology, dark matter is hypothetical matter of unknown composition that does not emit or reflect enough electromagnetic radiation to be observed directly, but whose presence can be inferred from gravitational effects on visible matter.
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In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. ^[1]
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Thermal radiation is electromagnetic radiation emitted from the surface of an object which is due to the object's temperature. Infrared radiation from a common household radiator or electric heater is an example of thermal radiation, as is the light emitted by a glowing
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An element's emission spectrum is the relative intensity of electromagnetic radiation of each frequency it emits when it is heated (or more generally when it is excited).

When the electrons in the element are excited, they jump to higher energy levels.
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black body is an object that absorbs all electromagnetic radiation that falls onto it. No radiation passes through it and none is reflected. It is this lack of both transmission and reflection to which the name refers.
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A material's absorption spectrum shows the fraction of incident electromagnetic radiation absorbed by the material over a range of frequencies. An absorption spectrum is, in a sense, the opposite of an emission spectrum.
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Electromagnetic spectroscopy, also known as spectrophotometry is the spectroscopy of electromagnetic spectra which arise out of atoms absorbing and emitting quanta of electromagnetic radiation.

Electromagnetic spectroscopy involves the use of a spectrophotometer.
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Untied States
Department of Commerce

Seal of the Department of Commerce
Agency overview
Formed February 14, 1903

Employees 36,000 (2004)
Annual Budget $9.
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Deputy Minister Richard Dicerni

Established 1993

Responsibilities CRTC

Copyright Board of Canada

Canadian Intellectual Property Office
Employees 6,104 (2006)
Department Website Industry Canada
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Ofcom is the independent regulator and competition authority for the communication industries in the United Kingdom^[1]. Ofcom was initially established in the enabling device, the Office of Communications Act 2002
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visible spectrum (or sometimes optical spectrum) is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light.
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For the music band, see .

Gamma rays or gamma-ray (denoted as γ) are forms of electromagnetic radiation (EMR) or light emissions of a specific frequency produced from sub-atomic particle interaction, such as electron-positron annihilation and
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X-rays (or Röntgen rays) are a form of electromagnetic radiation with a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 PHz to 30 EHz. X-rays are primarily used for diagnostic radiography and crystallography.
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