Radio Waves

Radio waves are used everyday, when talking on the phone, watching tv, or listening to the radio.
Radio waves are electromagnetic waves with frequenciese ranging from 3Hz to 300MHz on the electromagnetic spectrum.





Radio waves are used to transmit data from one area to another, e.g. from one cell phone to another cell phone, or from a radio station to a radio. It can also be used for radio astronomy which is the study of objects in space that emit radio waves. With radio astronomy, astronomical phenomena that are often invisible in other portions of the electromagnetic spectrum can be studied.


This composite image of the Whirlpool Galaxy, Messier 51, shows that the radio emission from the galaxy’s cold hydrogen gas (blue) extends well beyond the optical light emitted by its stars (Credit: NRAO/AUI, J. Uson).

Radio waves are being used when listening to the radio. AM (amplitude modulation) radios use frequencies from 535Hz to 1705HZ. The ionosphere is a layer of heavily charged ion molecules above the earth's atmosphere. A station's frequency (or channel), the power of the transmitter in watts, and ionospheric refraction all effect the distance an AM wave travels.The ionosphere is much more effective in reflecting/refracting these am radio waves at night. That's why at sunset most AM radio stations in the U.S. usually reduce power, directionalize their signal (send some of their signal in more directions than others), or go off the air until the next day.

FM (frequency modulation) radio waves range from 88MHz to 108MHz. These waves are not affected by ionospheric refraction and go in a straight line, this results in the waves going into space. They also can be stopped and reflected by buildings. These waves however do not have any of the problems of AM waves.

There are some safety concerns regarding potential radio wave dangers. Some people who work with radio waves have complained about headaches. Some people fear that they might get cancer from using their cell phones too much, but there not enough avalible scientific evidence to confirm this concern.

Since radio waves are electro magnetic waves, when they hit matter they exert forces on the charges of the atoms that make up the matter. Radio waves however, are very weak and usually not much happens when thay hit matter. In some metals though, the atomic electrons will be easily moved by a radio wave. This is why antennas work; the radio wave causes currents in the antenna which can be sent to a circuit which can convert the currents into the information that was sent by the radio wave if it was carrying information.

Bibliography
http://science.hq.nasa.gov/kids/imagers/ems/radio.html
http://www.nrao.edu/index.php/learn/radioastronomy/radiowaves
http://www.cybercollege.com/frtv/frtv017.htm
http://www.youtube.com/watch?v=1sfeua3YSLc
http://www.nrao.edu/index.php/learn/radioastronomy
http://wiki.answers.com/Q/How_does_radio_waves_interact_with_matter