Ionosphere
This exhibit requires that you get
Description:	Simulation of radio waves bouncing off / passing through the earth's ionosphere based on its wavelength.
To try this simulation:	Radio waves, shown here as spheres, are emitted from the satellite dish, and if they are too big they will be reflected by the earth's ionosphere. If they are small enough, they will pass through. Whether a radio broadcast passes through the ionosphere depends on the frequency & wavelength of the radio waves. Do one of the following: • Click left button to shorten the wavelength of the radio waves. Click right button to increase them. • Press left bracket ("[") to increase the wavelength of the radio waves. Press right bracket ("]") to shorten them. (NOTE: Click on the applet window first to activate it.)
What's Going On?	The Ionosphere is an electrically charged part of our atmosphere, 50 miles up and higher. Lower frequency radio waves are reflected by the ionosphere back to earth while microwaves (high-frequency radio waves) go right through on to space and or satellites. The height of the ionosphere is affected by sunlight, changing during the day as well as during the year, which alters radio reception on the earth's surface. Here, a metal grid represents the ionosphere. High frequency waves from one transmitter are small enough to pass through holes into the receiver at the upper left. Because the other transmitter has a lower frequency, the larger waves do not pass through the holes. These bounce off and head downward. When the height of the grid changes, waves are reflected at a different angle and miss the bottom receiver. Change the receiver's tilt and you intercept the reflected beam.
There's More!	If you listen carefully on the short-wave receiver (mostly in the afternoon and evenings) you can hear radio stations from as far away as Europe or the west coast of the US. The first long distance communication was accomplished by ionosphere bounce when Marconi transmitted a signal several thousand miles from England to Canada in 1901. It wasn't until 1924 that the reason for his success, the ionosphere, was discovered!
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