Electromagnetic radiation has some of the properties of both a particle and a wave. Particles have a definite mass and they occupy space.
Waves have no mass and yet they carry energy as they travel through space.
The idealized drawing of a wave in the figure below illustrates the definitions of amplitude and wavelength. Electromagnetic radiation energy can be seen as an oscillating wave of electric and magnetic fields traveling away from a source. The distance between the peaks of the wave is called the wavelength .