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The term radiation describes the propagation of particles or waves . In the first case one speaks of particle radiation or corpuscular radiation , in the second of wave radiation .

The distinction between particles and waves is historical and is still important as a clear statement. However, according to current knowledge, every radiation has both particle and wave properties (see also wave-particle dualism ).

Use of the word

Radiation , plural to beam , is sometimes used synonymously with radiation, including in compounds such as alpha and x-rays . A singular such as X-ray contrast, almost always refers to a bundle of rays , which directed and this energy and momentum transported. If the beam consists of particles with mass , charge or other properties, these are also transported. Light beam can, however , mean both, the idealized linear beam (see geometric optics ) or a bundle of rays. The ambiguity of the German word Strahl is also shown in the fact that there are several different expressions for it in other languages. In English, for example, ray denotes an imaginary, idealized ray, beam a bundle of rays and jet a ray of macroscopic matter.

The propagation of sound and other mechanical waves follows similar laws as the propagation of electromagnetic radiation . However, they are rarely referred to as radiation.


If the radiation hits an obstacle, it is either absorbed (absorbed and converted), transmitted unaffected (let through), scattered or reflected (thrown back).

The historical debate as to whether rays of light consist of particles or waves was answered in quantum physics by stating that a ray of light consists of photons , the location of which is described in the context of quantum mechanics by a probability wave . These probability waves can interfere with each other (see double slit experiment ). Louis de Broglie showed in his theory of matter waves that each particle can be assigned a wavelength . This explains why, for example, an electron beam also shows interference phenomena (see also wave-particle dualism ).


Radiation is differentiated according to its components, its source or its effect.

Electromagnetic waves

Electromagnetic waves are made up of photons . Electromagnetic waves with a short wavelength , i.e. high photon energy, are often referred to as electromagnetic radiation in everyday language . B. X-rays , bremsstrahlung , UV radiation , thermal radiation or infrared radiation . In the long-wave range, one speaks more of waves , such as radio waves .

Particle radiation

The terms particle radiation and corpuscular radiation are sometimes used as generic terms for radiation whose components have a mass other than zero .

Particle radiation is differentiated according to the type of particles it consists of, for example alpha radiation (α-particles), beta radiation (electrons or positrons) or neutron radiation .

Radiation from space

Radiation from space is differentiated according to its source, for example solar radiation , cosmic radiation , background radiation and Hawking radiation . Radiation emanating from radioactive substances is often incorrectly referred to as radioactive radiation , although it is not the radiation that is radioactive but the emitting substance. The radiation from the earth's natural radioactivity is called terrestrial radiation .

Ionizing radiation

If the energy of the radiation particles is so high that they can remove electrons from atoms or molecules, the radiation is known as ionizing radiation . Electromagnetic waves in this energy range often give off a large part of their energy on the first impact. For the energy and material dependency see mass attenuation coefficient . Charged particles with high energy release them in many small portions as they pass through matter. For the energy and material dependency, see braking capacity .

"Hard" and "soft" radiation

With different types of radiation, e.g. B. X-ray, gamma and beta radiation is sometimes referred to as “hard” (here synonymous with high-energy) or “soft” (lower-energy) radiation. However, there are no precise delimitations of these terms. Of hard X-rays , for example, in the X-ray optics speaking, if approximately the wavelength is shorter nm than the spacing of atoms in the solid, that is in the range 0.01 to about 0.5.

See also


  • Richard P. Feynman, Robert B. Leighton, Matthew Sands: Feynman - Lectures on Physics 2. Radiation and Heat, Walter de Gruyter GmbH, Berlin 2015, ISBN 978-3-11-036770-6 .
  • Stephan Kabelac: Thermodynamics of Radiation. Springer Fachmedien, Wiesbaden 1994, ISBN 978-3-663-12475-7 .
  • Christian Streffer: Radiation Biochemistry. Springer Verlag, Berlin / Heidelberg 1969.

Web links

Wiktionary: Radiation  - explanations of meanings, word origins, synonyms, translations