The electromagnetic spectrum is a spectrum that encompasses the range of wavelengths of [[Electromagnetic Radiation]]. 

The US government regulates license frequency ranges to be used as signals within this spectrum. Broadcast and [[Satellite]] [[TV]], [[AM]] and [[FM]] radio, your home [[WiFi]], [[Bluetooth]] devices and basically every piece of wireless electronics makes use of the principals of this spectrum.

For radio in the real world, behavior also depends on the [[Ionosphere]], which can absorb or bend some frequencies.