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Radio is the wirelesstransmission
of signals, by modulation of
electromagnetic waves with frequencies below
those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and
the vacuum of space. It does not require a medium of transport. Information is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude or their frequency.
When radio waves pass an electrical conductor, the oscillating fields induce an alternating current in the conductor. This
can be detected and transformed into sound or other signals that
carry information.
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