Revision:Infra-red Light

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Wavelength: 7.5 × 10-7m to 10-3m

Sources

All hot bodies.

Detection

Photographic plates, heat sensitive detectors (eg, thermometers), thermopiles.

Uses

Infrared radiation is mainly heat. All moderately hot bodies emit infrared. This is often used to detect human beings (which, being constantly at 310K, are considered hot) by groups like the army (for the killing of humans), and the police (for the prevention of the killing of humans). Firefighters also use infrared detectors to locate the sources of fires (which are naturally hotter than the blazes around them).

Infrared photography also enables pictures to be taken in the dark (no visible light) or in hazy conditions (when visible light is scattered more than infrared).

Infrared radiation is also used in optical fibres, like visible light. This was the original wavelength of the lasers used in this communications method. Infrared is also used for point to point communications.

Infrared is also used for therapeutic purposes.

Notes

The use of Infrared in computer communications is governed by the IrDA standard.

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