Monday, December 24, 2012

THE RADIO

The radio programsa re sent by a machine called a transmitter to your radio which is called a receiver. They are sent through the air over long distances by electromagnetic waves. These are the radio waves. These were discovered by a German scientist named Heinrich Hertz. He also discovered that the radio waves have different lengths.
         Then, Guglielmo Marconi invented a microphone, that changed sound waves into electronic signals, and developed a receiver that turned them back into the sound again.
A radio wave looked like a letter –s- lying on its side. Short waves curved up and down more times each second than longer ones. He divided all the waves according to how many times they curved or how frequently they curved. He called each group a frequency.
          At last, the scientists found that they could reduce static and other noise by using only the top half of a radio wave. This transmission is called FM broadcasting.

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