Rebecca Winn, age 10, of Peoria , Ill., for her question:
How do radio sounds travel without wires?
We need..no wires to hear the distant thunder but the sound takes several seconds to reach us. Teiephone talk travels almost a million times faster, but we need wires to carry the sound. Radio travels at the same speed as sounds by telephone, but no wires are needed to carry it along.
A radio program is somewhat like a present by parcel post. Someone wrapped the package and mailed it at the post office. The present is hidden in layers of brown paper and we loose sight of the package as it travels on its way to the right address. When it arrives, you open the wrappings and at last get a look at your present.
A radio program is wrapped up in the broadcasting studio and sent by carrier waves. When it leaves the station, the program seems to disappear because the carrier waves are silent and invisible. They travel at more than 650 million miles an hour and reach your radio set in less than a second. Vfen you turn on your set, the program is separated from its carrier waves. You then hear the voices and music that were wrapped up in the broadcasting station.
The mighty carrier waves make it possible for radio sounds and signals to travel without wires. They are ca11ed electromagnetic waves because they are related to electricity and to the invisible force that comes from a magnet. They radiate or fan out from a center in all directions at 186,000 miles a second and no one knows what makes them go go go. They cross the universe and our radio telescopes trap signals from stars that are trillions of miles away.
In a broadcasting studio, a transmitter changes the ordinary sounds of voices and music into electrical impulses. These silent signals are added to the carrier waves radiating out from the radio station's tall antenna. The carrier waves carry the hidden signals out in all directions at the speed of light. Those that go down are soon stopped by the solid ground. Some travel for a while in straight lines near the curved surface of the globe. Their signals can be picked up by radio sets near the station.
Some radio waves zoom up and strike a layer of the atmosphere ca11ed the ionosphere. Here the thin air teems with electrical particles that stop the radio waves and bounce them down again. These waves s1ope down and strike the earth maybe thousands of miles from the radio station. And when they strike your radio set, you can tune in the program that was wrapped up in the faraway broadcasting studio.
Radio waves are far, far more powerful than ordinary electrical current. In alternating currents of 60 cycles, busy electrons jog back and forth in the wires 60 times every second. Radio waves jog back and forth in kilocycles, which is thousands of times a second. When a radio announcer says that his program is broadcasting on 460 kilocycles, he means that the electrons that create the carrier waves are jogging back and forth at 460,000 times every second.