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radiation consisting of electromagnetic waves, including radio waves, infrared, visible light, ultraviolet, x-rays, and gamma rays.
THINGAMABOB OR THINGUMMY: CAN YOU DISTINGUISH BETWEEN THE US AND UK TERMS IN THIS QUIZ?
Do you know the difference between everyday US and UK terminology? Test yourself with this quiz on words that differ across the Atlantic.
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In the UK, COTTON CANDY is more commonly known as…
Origin of electromagnetic radiation
First recorded in 1950–55
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
British Dictionary definitions for electromagnetic radiation
radiation consisting of self-sustaining oscillating electric and magnetic fields at right angles to each other and to the direction of propagation. It does not require a supporting medium and travels through empty space at the speed of lightSee also photon
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Scientific definitions for electromagnetic radiation
Energy in the form of transverse magnetic and electric waves. In a vacuum, these waves travel at the speed of light (which is itself a form of electromagnetic radiation). The acceleration of electric charges (such as alternating current in a radio transmitter) gives rise to electromagnetic radiation. Other common examples of electromagnetic radiation are x-rays, microwaves, and radio waves. A single unit, or quantum, of electromagnetic radiation is called a photon. See also electromagnetism polarization.
A Closer Look
In the nineteenth century, physicists discovered that a changing electric field creates a magnetic field and vice versa. Thus a variation in an electric field (for example, the changing field created when a charged particle such as an electron moves up and down) will generate a magnetic field, which in turn induces an electric field. Equations formulated by James Clerk Maxwell predicted that these fields could potentially reinforce each other, creating an electromagnetic ripple that propagates through space. In fact, visible light and all other forms of electromagnetic radiation consist exactly of such waves of mutually reinforcing electric and magnetic fields, traveling at the speed of light. The frequency of the radiation determines how it interacts with charged particles, especially with the electrons of atoms, which absorb and reemit the radiation. The energy of the electromagnetic radiation is proportional to its frequency: the greater the frequency of the waves, the greater their energy. Electromagnetic radiation can also be conceived of as streams of particles known as photons. The photon is the quantum (the smallest possible unit) of electromagnetic radiation. In quantum mechanics, all phenomena in which charged particles interact with one another, as in the binding of protons and electrons in an atom or the formation of chemical bonds between atoms in a molecule, can be understood as an exchange of photons by the charged particles.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Cultural definitions for electromagnetic radiation
Any type of electromagnetic wave.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.