Infra-red

The infra-red radiation ( IR ) is a electromagnetic Rayonnement of a Wavelength higher than that of the Lumière visible but shorter than that of the Micro-onde S.


Definition

The name means “in on this side red” (of the Latin will infra : “in on this side”), because the infra-red is a wave of frequency lower than that of the red light (and thus wavelength higher than that of the red which goes from 500 to 700 Nm). The wavelength of the infra-red lies between 700 Nm and 1000 μm.

The infra-reds are subdivided out of IR close relations (0,7-5 μm), IR means (5-30 μm) and IR distances (30-1  000 μm). This classification is however not precise; each field of application has its own interpretation of the border between these various types.

The infra-reds are associated with the Chaleur because, with normal Température, the objects spontaneously emit radiations in the field of the infra-reds, the exact relation being given by the law of the radiation of the black Corps; in addition, the infra-red radiation puts in vibration the Atome S of the body which absorbs it and thus raises its temperature (transfer of Chaleur by Rayonnement). At first approximation, the wavelength of the maximum of emission of a black body carried to a absolute Température T is worth 2  898/T. That means that at room temperature (T around 300 K), the maximum of emission is at the neighborhoods of 10 micrometers. That poses specific problems in Astronomie in particular, because of the thermal Fond caused.

Uses

The lamps has Infra Rouge are used in fields of the daily production. The sectors of the Car, the Agro Food one, the textiles, Plasturgie, the Formatting of matters, care of body etc are concerned with applications of matter heating.

These particular and innovating techniques of heat allow a productivity gain and an economy of the production costs which are characterized in saved time and energy spent. All the German automobile Large companies of production and in the world are equipped gradually with these new tools has strong profitability.

A site created by Philips gives accurate informations on these applications (http://www.iwtinfrarouge.com/images/pdf/Philips_catalogue_fr.pdf)

Also Heraus has this http://www.heraeus-noblelight.com/fr/nouvelles.html?no_cache=1 address

or here on permanent and adapted technologies of production all the cases have: http://www.iwtinfrarouge.com

concurrently to this industrial sector, The infra-reds are used in the equipment of Vision of night, when the quantity of light is so weak, that one cannot even amplify it sufficiently, to see the objects. The radiation is detected then posted on a screen, the hottest objects becoming also most luminous. It is also necessary to add like use, in addition to the vision of night, all the field of the infra-red Thermographie making it possible to see and measure remotely and without contact the temperature of target objects. In certain cases a projector of infra-red associated with the system with vision, makes it possible to visualize objects without intrinsic heat, by reflection.

The infra-reds are also used in the military field for the guidance of the Missile S air-to-air or anti-aircraft: an infra-red detector then guides the missile towards the source of heat which constitutes to it (or them) engine of the target plane. Such missiles can be avoided by special operations (alignment with the Sun) or by the use of thermal lures.

A more common use is their use in the remote controls (Télécommande S), where they are preferred with the waves radio, because they do not interfere with the other electromagnetic signals like the signals of television. In this field, there exist several codings of information (RC5 for Philips, SIRSC for Sony, etc). The infra-reds are also used for the communication at short distance between the Ordinateur S and their peripheral. The apparatuses using this type of communication are generally in conformity with the standards published by the Infrared Data Association (IrDA).

The light used in the fiberoptics is generally of the infra-red. For this application, one exploits the wavelengths where the clean absorption of material constituting fiber is minimal: 1,3 µm and 1,55 µm.

They are very much used in the field of the Robotique or in the apparatuses requiring of the data transmissions at short distance without obstacle.

Moreover, the infra-red Spectroscopie is one of the most effective methods (and one of most widespread) for the identification of the Molécule S organics and inorganic starting from their vibrationnelles properties. Indeed, the infra-red radiation excites modes of vibration (deformation, elongation) specific of chemical bonds. The comparison between radiation incidental and transmitted through the sample is consequently enough to determine the principal chemical functions present in the sample.

The infra-red Astronomie is difficult because of the terrestrial atmosphere. Therefore the astronomers send satellite infra-red: WILL GO (1983; NASA, the United Kingdom, Netherlands), ISO (1995; ESA), Wire (1999; The USA, failure with launching), Spitzer (2003; ex-SIRTF, the USA), ASTRO-F (2006; Japan) and the future Herschel (2008? ; ESA).

Today, the infra-red raies are also used for the control of banknote authenticity . In this manner, they lend themselves particularly for the detection of counterfeit bills .

History

The infra-red radiation is intuitively perceptible by the simple exposure of the skin to the sun or the heat emitted by an hot source in the black, but it was not proven in 1800 by William Herschel, a astronomer English of German origin , by means of a very simple experiment: Herschel had the idea to place a Thermomètre at mercury in the spectrum obtained by a prism of glass in order to measure specific heat to each color. The thermometer indicates that received heat is strongest on the side of the red of the spectrum, including beyond the visible zone of light, where there was no more light. It was the first experiment showing that heat could be transmitted by an invisible form of light.
Il has in same shown time that a prism could deviate a heating ray.

See too

  • Detection of counterfeit bills using the infra-red

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