Q.: How long is a radio wave...

Q.: How long is a radio wave and how do you measure it?

A.: Radio waves come in a variety of lengths, from as short as an inch or less to as long as several miles, according to astrophysicist Sterl Phinney of Caltech. The waves we usually think of as radio waves, the ones that broadcast music and news, range in length from about 10 feet for FM to about 300 yards for AM.

Scientists measure their length by counting the numutingthe number that go by in a given time interval, Phinney said. Radio waves move at the speed of light, about 300 million meters per second. For an FM station at 100.0 on the dial, 100 million wave-lengths go by in each second,s o they wave-length is 300 million-100 million=3 meters, or about 10 feet.