The radiation is a transfer of energy in the form of Onde S or of particle S, which can occur by electromagnetic Rayonnement (for example: Infra-red) or by a Disintegration (for example: Radioactivity α). Consequently, the transfer can be carried out in the vacuum. The example characteristic of radiation is that of the Sun in space.

In Physical, the term radiation or its synonym radiation indicates the process of emission or transmission of energy in the form of particles or electromagnetic waves, or acoustic waves. It includes/understands electromagnetic radiations (radio waves, Infrarouge, Lumière, X-rays, Gamma rays) as well as the particulate radiations (particles alpha, beta, Neutron S).

The term of “radiation” also indicates the energy thus emitted and propagated, which is also called “radiant energy”. One also speaks about radiation Lumineux, and heating radiation.

The radiation is, with the thermal Conduction and the convection (forced Convection or natural Convection), one of the three modes of transfer of heat.

In the common direction, the term “radiation” is associated with the Radioactivité, that thus relates to the ionizing rays (x-rays, α, β, γ). The irradiation consists in being subjected to Ionizing rays, whereas the radioactive Contamination indicates the absorption of radioactive materials which cause an irradiation inside the organization. An object or an irradiated body does not become in general radioactive itself, unless the irradiation did not cause the manufacture of unstable cores (for example the Fuel nuclear is not very radioactive before use, but very radioactive afterwards).

In nuclear industry, the workers are provided with instruments allowing to measure the daily amount of radiation received by each individual.

Use of the term

Various expressions are derived from the concept of radiation:

• the cultural Radiation , indicates the diffusion of a Culture in the world.

• the international radiation of an Unintermitting , a country, an area, a city indicates not only the Rayonnement cultural, but also the radiation in the economic domain, social,…: the international radiation of the town of Lyon

• a “radiation source” is a process by which the transformation of a form of energy occurs into radiant energy. This term also indicates a material system (apparatus, substance) suitable for carry out this transformation.

• a radiation “Monochromatique” or “simple” is defined by its Wavelength when it is propagated in the Matière or the Vide. Such a radiation transports energy at the speed of the Lumière. But this energy is not directly measurable in its radiant form. It should be transformed to make it measurable. The easiest transformation is the transformation of the radiation into Chaleur.

• a “complex” radiation is a formed radiation of a sum of simple radiations, from which the wavelengths and the energy S can be different. The traditional experiment of Isaac Newton, which gives Solar light a spectrum of radiations “coloured” by refraction through a prism of glass, is the first goes back to it to have highlighted the dispersion of the optical radiation. The method of the prism is still currently one of those used for the study of the dispersion of radiations, i.e. for the measurement of the Index of refraction of a material according to the wavelength of the incidental radiation. The spectrum obtained, visible field of the electromagnetic Spectrum, “improperly” is called Visible spectrum .

• corpuscular” or “particulate” radiation a “is a radiation considered as primarily formed by trajectories of particle S neutrals or electrified. The particulate radiations are often indicated by the word radiation followed by an adjective or a Greek letter pointing out the nature of the constitutive particles (alpha radiation, béta, gamma). The concept of corpuscular radiations is resulting from the study of the rays resulting from radioactive substances and the analysis of the electric shock through the Gaz rarefied S led to discovered radiations of very an other nature that known periodic radiations up to that point.

• an “electromagnetic” radiation is a radiation characterized by variations of fields electric and magnetic. The electromagnetic radiations include/understand, by order of quantum energy increasing, the Hertzian waves, the infra-red raies, the visible Lumière, the ultraviolet rays, the x-rays, the gamma rays and the cosmic rays. The Gamme of frequencies (or wavelengths) constitutes the electromagnetic Specter.

• Light: The Infra-red radiation, visible radiation, Ultraviolet radiation.
• Radiation gamma.

• the “cosmic” radiation in Astronomy, is synonymous with cosmic radiation.

• the “ionizing” radiation indicates the radiations able to ionize the atoms and molecules, so known under the name of ionizing Radiation. Conversely, the radiations which are unable are called radiations not-ionizing S.

• the continuous Radiation of braking ( Bremsstrahlung ), in Astronomy and electromagnetism, is the electromagnetic Rayonnement produces by the deceleration or the acceleration of charged particle S, at the time of their passage in the Electric field of cores or other particles charged. This deceleration of accelerated particles and in particular of the electron S, by passage in the vicinity of centers charged produces an electromagnetic radiation explains the continuous spectrum X-rays.

• the “black” radiation is the radiation of the black Corps. The law of distribution of the black radiation, the Loi of Planck, is the formula representing the spectral distribution of the energy of the radiation between different the wavelengths which are present there.

• the solar radiation, in Meteorology, indicates solar radiation.

• the terrestrial radiation, in Meteorology, indicates the radiation emitted by the Ground, including the atmosphere.

• the thermal radiation, in Thermodynamic, indicates the electromagnetic radiation coming from the thermal energy conversion (see black Corps and Infrarouge).

• the “pressure of radiation”, in Astronomy, indicates the Pression of radiation.

Effect on the alive one

See Ionizing rays and not-ionizing Radiation.

See too

• Light
• evolutionary Radiation, term of zoology