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| If you're in a room with a window, go open the
window. Then come back. If you're not in a room with a
window, just wait quietly. |
| Finished? Good. You just let all of the radio
waves into the room. |
| Radio waves are constantly traveling through
the air in your community. They're invisible, like light
waves. Together, radio and light waves are part of the
spectrum of electromagnetic energy. The radio waves are the
longest in the spectrum, making them easiest to generate and
transmit over long distances. This physical property makes
radio waves an ideal means of communication. |
| Do you have a radio? You know, an
old-fashioned AM/FM radio? Inside your radio is a "receiver"
which receives and translates the communication signals
carried on the radio waves that are traveling through the
air in your community. Each "radio station" in your
community transmits radio waves at their own unique
"frequency." That way, you can tune in and receive their
radio waves instantly. Or, what seems instant to our ears.
Radio waves travel at the "speed of light," 186,282 miles
per second. So, when your team's star hitter swings the bat
and sends the baseball soaring out of the stadium, the radio
announcer's excited cry reaches your radio just a tiny
little fragment of a second later. |
| The air in your community and in your room is
an ideal "transmitter" of the radio waves. The air allows
the radio waves to travel comfortably through. Many
materials, however, do not allow the radio waves to travel
through; rather they "reflect" the radio waves, causing them
to bounce back. The metal of an airplane's wing, the rock of
a mountain, and the water in a storm cloud are all
reflective materials. When radio waves hit them, the waves
bounce back. |
| These properties of materials and of radio
waves made RADAR
possible. |
