Radiation is more than just the invisible stuff that nuclear bombs leave behind. Ultraviolet, microwave, infrared, FM radio signals, visible light; These are all considered radiation. The EM spectrum refers to all of the different types of radiation that exist. It arranges these types of radiation in order by their wavelengths. The wavelength of a wave is the distance between 2 consecutive peaks. Radiation in the EM spectrum is made up of waves that contain an Electric field and a Magnetic field (see figure below). EM radiation is naturally transmitted by stars (including our sun), travels at the speed of light, and can vary in wavelengths from 0.000000000001 meter (Gamma rays) to 10,000 m (television & radio)! In theory, the possible wavelengths extend in size to infinitely large and small. The frequency of a wave may be defined by how often the wave ÒpeaksÓ pass a fixed point in space in 1 second. For example, 1 peak/second = 1 Hz; 10 peaks/second = 10 Hz. The frequency of any wave can be calculated by dividing the speed of light (3*108 m/s) by the wavelength. For example:

The frequency of the EM waves transmitted by WHFS (a D.C. based modern Rock FM radio station) is 99.1 Mhz. That's where you'll actually find the station on your radio; at 99.1.
The speed of light is 3*10^8 m/s.
So....the wavelength of the EM radiation put out by the WHFS transmitter is
wavelength = (3*108[m/s]) /(99100000 [1/sec]) = 3.02 meters