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Hyperphysics: Electromagnetic Waves
In the photo above of a handheld citizens band radio, the metal coil is the antenna. When the radio is transmitting, the radio produces an electric current that surges back and forth in the antenna, which emits radio waves. And when the radio is receiving, radio waves induce a tiny alternating current in the antenna. The current in the antenna carries the radio signal.
For a drawing of an electromagnetic wave (radio waves are one example) see Hyperphysics: Electromagnetic Waves. To learn more about the CB antenna shown in the photo, go to this Wikipedia article and scroll down.
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PhET Simulation: Radio Waves & Electromagnetic Fields
Once you have clicked on the "simulation" link below, be sure to read the Java Security Advisory before running the simulation: To do that, click the "Read now" button on the yellow band near the top of the PhET page.
Shake a charged particle, and it radiates electromagnetic waves. You can try this out with the PhET Simulation: Radio Waves & Electromagnetic Fields. Compare with Physics in Your World above.
To learn more, check out these Physics 2000
(This feature was updated on May 5, 2013.)