What makes a wave electromagnetic?
A wave is, loosely speaking, transfer of energy without any transfer
of matter. Generally wave propagation is associated with vibration
or oscillation of some physical quantity about a mean : for example
pressure in a sound wave. If electromagnetic field is the physical
quantity which is oscillating, for simplicity consider this oscillation
in absence of charges, then the wave is electromagnetic. Light,
X-rays, ultraviolet radiation, radio waves are all electromagnetic
waves with different wavelength.
Click here to return to the Physics Archives
Update: June 2012