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radio wave

 
Dictionary: radio wave

n.
An electromagnetic wave within the range of radio frequencies.


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Radio waves lie at the low-frequency end of the electromagnetic spectrum. They are primarily used …
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Radio waves lie at the low-frequency end of the electromagnetic spectrum. They are primarily used … (credit: © Merriam-Webster Inc.)
Wave from the portion of the electromagnetic spectrum at lower frequencies than microwaves. The wavelengths of radio waves range from thousands of metres to around 30 cm. These correspond to frequencies as low as 3 Hz and as high as 1 gigahertz (109 Hz). Radio-wave communications signals travel through the air in a straight line, reflect off of clouds or layers of the ionosphere, or are relayed by satellites in space. They are used in standard broadcast radio and television, short-wave radio, navigation and air-traffic control, cellular telephony, and even remote-controlled toys.

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Science Dictionary: radio waves
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Waves at the end of the electromagnetic spectrum with the lowest frequency (less than 300 megahertz) and the longest wavelength (from a few feet to many miles). Because of their low frequency, radio waves carry very little energy compared to other electromagnetic waves. (See Planck's constant.)

  • Radio waves can pass through the atmosphere and therefore are very useful for communication. Commercial, short-wave, and citizens' band radio are broadcast with radio waves, as is television.
  • Wikipedia: Radio waves
    Top

    Radio waves are that part of the electromagnetic spectrum with wavelengths longer than infrared light. Naturally-occurring radio waves are produced by lightning, or by astronomical objects. Artificially-generated radio waves are used for broadcasting, mobile and fixed communications, navigation, computer networks and innumerable other applications. Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves may cover a part of the Earth very consistently, shorter waves can reflect off the ionosphere and travel around the world, and much shorter wavelengths bend or reflect very little and travel on a line of sight.

    Diagram of the electric (E) and magnetic (H) fields of Radio Waves emanating from a radio transmitting antenna (small dark vertical line in the center). The E and H fields are perpendicular as implied by the phase diagram in the lower right.

    Contents

    Discovery and utilization

    Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including radio waves.

    Radio waves were first predicted by mathematical work done in 1865 by James Clerk Maxwell. Maxwell noticed wavelike properties of light and similarities in electrical and magnetic observations. He then proposed equations, that described light waves and radio waves as waves of electromagnetism that travel in space. In 1887, Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory. Many inventions followed, making practical the use of radio waves to transfer information through space.

    Propagation

    The study of how electromagnetic phenomena such as reflection, refraction, polarization, diffraction and absorption is of critical importantance in the study of radio waves move in free space and over the surface of the Earth. Different frequencies experience different combinations of these phenomena in the Earth's atmosphere, making certain radio bands more useful for specific purposes than others.

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    Copyrights:

    Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
    Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
    Science Dictionary. The New Dictionary of Cultural Literacy, Third Edition Edited by E.D. Hirsch, Jr., Joseph F. Kett, and James Trefil. Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin. All rights reserved.  Read more
    Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Radio waves" Read more