electromagnetic radiation

electromagnetic radiation Energy arising from the acceleration of electrically charged entities (e.g. electrons). Electromagnetic radiation can be considered to be composed of waves or particles, since it displays properties of both; this is referred to as the wave–particle duality. Electromagnetic waves are composed of oscillating electric and magnetic fields which lie at right angles to each other and to the direction of travel. They propagate through a vacuum at the speed of light, c; the speed is slower when travelling through a medium such as air, water, or glass. The waves have a wavelength, λ, and a frequency, f or ν, which are linked by the equation c = f λ. Electromagnetic radiation may also be regarded as being composed of a stream of particles of zero mass called photons. The energy, E, of a photon is related to frequency by Planck's formula E = hf, where h is the Planck constant. Hence the higher the frequency, the greater the energy of the radiation.