Pub. date: 2008 | Online Pub. Date: April 25, 2008 | DOI: 10.4135/9781412963893 | Print ISBN: 9781412958783 | Online ISBN: 9781412963893| Publisher:SAGE Publications, Inc.About this encyclopedia
RADIATION IS ENERGY transmitted by electromagnetic waves. Electromagnetic waves travel at the speed of light (when passing through a vacuum) and have a characteristic wavelength, λ, which is inversely proportional to their frequency, v, by where c is the speed of light. Electromagnetic radiation is conceptualized in contemporary theory both as a wave and as a stream of particles called photons (this dual approach is referred to as wave-particle duality). The energy of any photon, E, of radiation is inversely proportional to the wavelength by where h is Planck's constant. This relationship allows us to order electromagnetic waves from high energy/short wavelength (for example, x-rays), to low energy/long wavelength (for example, radio waves). The resulting progression is referred to as the electromagnetic spectrum ( Figure 1 ). The visible region of the electromagnetic spectrum is bound by infrared (IR) radiation on ...