electromagnetic wave

An electromagnetic wave is an electric field and associated magnetic field spreading in wavelike-fashion through space at a speed of about 300,000 km/s, with its direction and intensity at any point in space oscillating rapidly back and forth. James Clerk's Maxwell's theory in 1864 suggested that light was such a wave, and today we know that such waves include all forms of light – also infrared and ultraviolet, as well as radio waves, microwaves, X-rays and gamma rays.


See also electromagnetic radiation and electromagnetic spectrum.