Electromagnetic radiation

In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space.^[1]^[2] It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ranging from radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.^[3]^[4] All forms of EMR travel at the speed of light in a vacuum and exhibit wave–particle duality, behaving both as waves and as discrete particles called photons.

Electromagnetic radiation is produced by accelerating charged particles such as from the Sun and other celestial bodies or artificially generated for various applications. Its interaction with matter depends on wavelength, influencing its uses in communication, medicine, industry, and scientific research. Radio waves enable broadcasting and wireless communication, infrared is used in thermal imaging, visible light is essential for vision, and higher-energy radiation, such as X-rays and gamma rays, is applied in medical imaging, cancer treatment, and industrial inspection. Exposure to high-energy radiation can pose health risks, making shielding and regulation necessary in certain applications.

In quantum mechanics, an alternate way of viewing EMR is that it consists of photons, uncharged elementary particles with zero rest mass which are the quanta of the electromagnetic field, responsible for all electromagnetic interactions.^[5] Quantum electrodynamics is the theory of how EMR interacts with matter on an atomic level.^[6] Quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation.^[7]

^ * Purcell and Morin, Harvard University. (2013). Electricity and Magnetism, 820p (3rd ed.). Cambridge University Press, New York. ISBN 978-1-107-01402-2. p 430: "These waves... require no medium to support their propagation. Traveling electromagnetic waves carry energy, and... the Poynting vector describes the energy flow...;" p 440: ... the electromagnetic wave must have the following properties: 1) The field pattern travels with speed c (speed of light); 2) At every point within the wave... the electric field strength E equals "c" times the magnetic field strength B; 3) The electric field and the magnetic field are perpendicular to one another and to the direction of travel, or propagation."
^ "What Is Electromagnetic Radiation?". ThoughtCo. Archived from the original on 25 September 2024. Retrieved 25 September 2024.
^ Maxwell, J. Clerk (1 January 1865). "A Dynamical Theory of the Electromagnetic Field". Philosophical Transactions of the Royal Society of London. 155: 459–512. Bibcode:1865RSPT..155..459M. doi:10.1098/rstl.1865.0008. S2CID 186207827.
^ * Browne, Michael (2013). Physics for Engineering and Science, p427 (2nd ed.). McGraw Hill/Schaum, New York. ISBN 978-0-07-161399-6.; p319: "For historical reasons, different portions of the EM spectrum are given different names, although they are all the same kind of thing. Visible light constitutes a narrow range of the spectrum, from wavelengths of about 400-800 nm.... ;p 320 "An electromagnetic wave carries forward momentum... If the radiation is absorbed by a surface, the momentum drops to zero and a force is exerted on the surface... Thus the radiation pressure of an electromagnetic wave is (formula)."
^ "The Dual Nature of Light as Reflected in the Nobel Archives". nobelprize.org. Archived from the original on 15 July 2017. Retrieved 4 September 2017.
^ "Electromagnetic Spectrum facts, information, pictures | Encyclopedia.com articles about Electromagnetic Spectrum". encyclopedia.com. Archived from the original on 13 June 2017. Retrieved 4 September 2017.
^ Tipler, Paul A. (1999). Physics for Scientists and Engineers: Vol. 1: Mechanics, Oscillations and Waves, Thermodynamics. MacMillan. p. 454. ISBN 978-1-57259-491-3.

[1] * Purcell and Morin, Harvard University. (2013). Electricity and Magnetism, 820p (3rd ed.). Cambridge University Press, New York. ISBN 978-1-107-01402-2. p 430: "These waves... require no medium to support their propagation. Traveling electromagnetic waves carry energy, and... the Poynting vector describes the energy flow...;" p 440: ... the electromagnetic wave must have the following properties: 1) The field pattern travels with speed c (speed of light); 2) At every point within the wave... the electric field strength E equals "c" times the magnetic field strength B; 3) The electric field and the magnetic field are perpendicular to one another and to the direction of travel, or propagation."

[ThoughtCo-2] "What Is Electromagnetic Radiation?". ThoughtCo. Archived from the original on 25 September 2024. Retrieved 25 September 2024.

[3] Maxwell, J. Clerk (1 January 1865). "A Dynamical Theory of the Electromagnetic Field". Philosophical Transactions of the Royal Society of London. 155: 459–512. Bibcode:1865RSPT..155..459M. doi:10.1098/rstl.1865.0008. S2CID 186207827.

[4] * Browne, Michael (2013). Physics for Engineering and Science, p427 (2nd ed.). McGraw Hill/Schaum, New York. ISBN 978-0-07-161399-6.; p319: "For historical reasons, different portions of the EM spectrum are given different names, although they are all the same kind of thing. Visible light constitutes a narrow range of the spectrum, from wavelengths of about 400-800 nm.... ;p 320 "An electromagnetic wave carries forward momentum... If the radiation is absorbed by a surface, the momentum drops to zero and a force is exerted on the surface... Thus the radiation pressure of an electromagnetic wave is (formula)."

[5] "The Dual Nature of Light as Reflected in the Nobel Archives". nobelprize.org. Archived from the original on 15 July 2017. Retrieved 4 September 2017.

[6] "Electromagnetic Spectrum facts, information, pictures | Encyclopedia.com articles about Electromagnetic Spectrum". encyclopedia.com. Archived from the original on 13 June 2017. Retrieved 4 September 2017.

[Tipler-7] Tipler, Paul A. (1999). Physics for Scientists and Engineers: Vol. 1: Mechanics, Oscillations and Waves, Thermodynamics. MacMillan. p. 454. ISBN 978-1-57259-491-3.

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