Radio is the wireless transmission of signals through free space by electromagnetic radiation of a frequency significantly below that of visible light, in the radio frequency range, from about 30 kHz to 300 GHz. These waves are called radio waves. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space.
Information, such as sound, is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.
Famous quotes containing the word radio:
“There was a girl who was running the traffic desk, and there was a woman who was on the overnight for radio as a producer, and my desk assistant was a woman. So when the world came to an end, we took over.”
—Marya McLaughlin, U.S. television newswoman. As quoted in Women in Television News, ch. 3, by Judith S. Gelfman (1976)
“A liberal is a socialist with a wife and two children.”
—Anonymous. BBC Radio 4 (April 8, 1990)
“The radio ... goes on early in the morning and is listened to at all hours of the day, until nine, ten and often eleven oclock in the evening. This is certainly a sign that the grown-ups have infinite patience, but it also means that the power of absorption of their brains is pretty limited, with exceptions, of courseI dont want to hurt anyones feelings. One or two news bulletins would be ample per day! But the old geese, wellIve said my piece!”
—Anne Frank (19291945)