Electromagnetic spectrum

Electromagnetic spectrum
Inductiveload, NASA · CC BY-SA 3.0 · source
Name	Electromagnetic spectrum
Type	Physical phenomenon
First described	19th century

Contents

Electromagnetic spectrum is the range of all possible electromagnetic radiation frequencies and wavelengths, encompassing waves from the longest radio wavelengths to the shortest gamma rays. It underpins technologies and sciences including Radio telescope, Hubble Space Telescope, CERN, National Aeronautics and Space Administration, and European Space Agency, and connects experimental work by figures such as James Clerk Maxwell, Heinrich Hertz, Wilhelm Röntgen, Max Planck, and Albert Einstein. Measurements and standards are maintained by institutions like International Bureau of Weights and Measures, National Institute of Standards and Technology, and practiced in laboratories at Caltech, MIT, Harvard University, Stanford University, and University of Cambridge.

Overview

The spectrum organizes electromagnetic radiation by frequency and wavelength, framing observations by observatories such as Very Large Array, Atacama Large Millimeter Array, and Arecibo Observatory, and informing missions like Voyager program, Pioneer program, and James Webb Space Telescope. It is central to technologies developed by companies and labs including Bell Labs, IBM, Intel, Siemens, and Lockheed Martin, and to standards from organizations such as Institute of Electrical and Electronics Engineers and International Telecommunication Union.

Classical theory derives from Maxwell’s equations formulated by James Clerk Maxwell and expanded in quantum treatments by Niels Bohr, Erwin Schrödinger, and Paul Dirac. Key properties include frequency, wavelength, energy (photon energy E = hν, where h was introduced by Max Planck), polarization investigated by Augustin-Jean Fresnel and Thomas Young, and propagation affected in media studied by Michael Faraday and Lord Kelvin (William Thomson). Quantum electrodynamics developed by Richard Feynman, Julian Schwinger, and Sin-Itiro Tomonaga explains interactions at particle accelerators like Fermilab and SLAC National Accelerator Laboratory. Dispersion, refraction, absorption, and scattering are treated in works by Johannes Kepler, Christiaan Huygens, and Leonhard Euler and applied in facilities such as Bell Labs and Rutherford Appleton Laboratory.

The classification includes radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma-ray bands used in instruments at Green Bank Observatory, NOAA, European Southern Observatory, Chandra X-ray Observatory, and Fermi Gamma-ray Space Telescope. Visible light studies draw on observatories like Palomar Observatory and museums such as Smithsonian Institution, while infrared surveys employ Spitzer Space Telescope and Infrared Astronomical Satellite. Ultraviolet research features Hubble Space Telescope programs and instruments at European Space Agency. X-ray and gamma-ray astronomy engage facilities like Chandra X-ray Observatory, XMM-Newton, and INTEGRAL.

Natural sources include the Sun, Milky Way, Pulsar, Quasar, Supernova, and Gamma-ray burst, observed by missions such as SOHO, Kepler, GALEX, and Swift Observatory. Artificial sources include transmitters at AT&T, Nokia, Motorola, microwave ovens manufactured by Panasonic Corporation, synchrotron facilities at Diamond Light Source and ESRF, X-ray tubes invented by Wilhelm Röntgen and particle interactions at CERN. Laser sources developed by Theodore Maiman and refined by Gordon Gould and Charles Townes span visible to infrared, while radio frequency generation is foundational to projects at Marconi Company and Radar research from World War II labs.

Detectors range from antenna arrays used by Karl Jansky and Guglielmo Marconi to photomultiplier tubes developed with contributions from Harold Hopkins and CCDs pioneered at Bell Labs and deployed on Hubble Space Telescope. X-ray detection uses instruments at Chandra X-ray Observatory and European Space Agency missions, while gamma-ray detection was advanced by experiments at CERN and the Fermi Gamma-ray Space Telescope. Spectrometers trace to designs by Joseph von Fraunhofer and William Huggins, interferometers to Albert A. Michelson, and bolometers to work at Caltech and Jet Propulsion Laboratory.

Applications span communication systems by AT&T, Verizon Communications, and Vodafone Group, medical imaging at hospitals like Mayo Clinic and Johns Hopkins Hospital (CT, MRI, X-ray), remote sensing by Landsat and Copernicus Programme, astronomy at Keck Observatory and Mauna Kea Observatories, manufacturing using lasers by firms such as TRUMPF and Coherent, Inc., and defense systems deployed by Northrop Grumman and Raytheon Technologies. Spectroscopy underpins chemistry in labs at Royal Society of Chemistry and pharmaceuticals at Pfizer and Roche.

Standards and guidelines come from World Health Organization, International Commission on Non-Ionizing Radiation Protection, and Occupational Safety and Health Administration. Medical dosimetry follows protocols developed by American Association of Physicists in Medicine, while radiation protection principles trace to work by Marie Curie and Hermann Joseph Muller. Public policy and regulation involve Federal Communications Commission, European Commission, and national health ministries.

Key milestones include theoretical synthesis by James Clerk Maxwell, experimental validation by Heinrich Hertz, discovery of X-rays by Wilhelm Röntgen, radioactivity by Henri Becquerel and Marie Curie, and quantum explanations by Max Planck and Albert Einstein. Instrumental advances occurred at Bell Labs, Los Alamos National Laboratory, Brookhaven National Laboratory, and observatories like Royal Greenwich Observatory and Mount Wilson Observatory. Measurement systems were standardized by International Bureau of Weights and Measures and international agreements coordinated through International Telecommunication Union.