ElectroMagnetic Radiation

Most waves need a medium to travel through and can not exist on there own or travel through a vacuum.  Electromagnetic waves such as light are different they can move through a vacuum such as space.  They do this by combining two separate waves electric and magnetic.  These waves are at right angles to each other and travel together through space at the speed of light.
  Electromagnetic wave moving to the right.
The wave moves in the direction of the arrow while the Red sin wave represents the electric field while the Blue represents the magnetic field.  Antennas convert signals in the from of current into electromagnetic waves which can then be intercepted by other antennas and converted back to a current which delivers the signal.

While all electromagnetic waves move at the same speed they are of different lengths.  The length of one cycle of the wave is called its wave length.  Since the waves move at the same speed a wave of long wave lenght will have fewer complete waves pase a given point then one of shorter wavelength.  The fallowing table shows some wave lengths and what they are used for.

taken from ( http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html )

Home         Forward to Simple Antennas,  Complex Antennas