Medium of propagation

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The propagation medium or short- medium designated in physics and technology a support for the propagation of a signal or a physical appearance.

In wave theory, a medium is something that is capable of propagating waves . In an electrical circuit , a medium is something that has mobile charge carriers and is therefore capable of transporting electrical charges .

While sound waves need a substance to propagate , electromagnetic waves (e.g. light ) can propagate in a vacuum . There is no such thing as an ether assumed to be a material carrier in earlier times .

In technology, bodies are also referred to as the propagation medium, which, due to their material and shape, enable the bundled propagation of waves.

Electromagnetic waves, optics

An electromagnetic wave propagates in a medium at a speed that is always lower than the speed of light in a vacuum . Every real medium causes a (wavelength-dependent) attenuation of the light. The permittivity and the magnetic permeability are characteristic of the transmission properties of the medium . Both properties are also dependent on the wavelength.

With waveguides such as coaxial cables , waveguides or optical waveguides , further parameters play a role, for example diameter and terminating resistance .

Depending on the wavelength and dimensions of the medium, the propagation is described with quantum physics , optics , line theory or electrical engineering.

Sound waves, acoustics

Sound waves can propagate in various media, namely in fluids (e.g. air , water ) or in solids (e.g. steel ). Accordingly, a distinction is made between fluid-borne sound (e.g. air- borne sound or water- borne sound ) and structure-borne sound .

Electrical current

The electrical current is usually formed by moving electrons and guided in an electrical conductor . However, charge carriers (i.e. any charged particles) can also move in liquids, gases, plasmas or in a vacuum.

Individual evidence

  1. IEC 60050, see DKE German Commission for Electrical, Electronic and Information Technologies in DIN and VDE: International Electrotechnical Dictionary - IEV entry 704-02-01.
  2. IEV entry 701-01-02.
  3. IEV entry 121-12-02.
  4. Ulrich Freyer: Media technology: basic knowledge of communications technology, terms, functions, applications . Hanser, 2013, chap. 8th.