to an advanced stage or point; "a young man who will go very far"
at or to a certain point or degree; "I can only go so far before I have to give up"; "how far can we get with this kind of argument?"
at or to or from a great distance in space; "he traveled far"; "strayed far from home"; "sat far away from each other"
being of a considerable distance or length; "a far trek"
being the animal or vehicle on the right or being on the right side of an animal or vehicle; "the horse on the right is the far horse"; "the right side is the far side of the horse"
beyond a norm in opinion or actions; "the far right"
located at a great distance in time or space or degree; "we come from a far country"; "far corners of the earth"; "the far future"; "a far journey"; "the far side of the road"; "far from the truth"; "far in the future"
remote in time; "if we could see far into the future"; "all that happened far in the past"
to a considerable degree; very much; "a far far better thing that I do"; "felt far worse than yesterday"; "eyes far too close together"
having or employing wavelengths longer than light but shorter than radio waves; lying outside the visible spectrum at its red end; "infrared radiation"; "infrared photography"
electromagnetic radiation with wavelengths longer than visible light but shorter than radio waves (同)infrared_light, infrared_radiation, infrared emission
the infrared region of the electromagnetic spectrum; electromagnetic wave frequencies below the visible range; "they could sense radiation in the infrared" (同)infrared frequency
the syllable naming the fourth (subdominant) note of the diatonic scale in solmization
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Diagram of part of the electromagnetic spectrum
Far infrared (FIR) is a region in the infrared spectrum of electromagnetic radiation. Far infrared is often defined as any radiation with a wavelength of 15 micrometers (µm) to 1 mm (corresponding to a range of about 20 THz to 300 GHz), which places far infrared radiation within the CIE IR-B and IR-C bands.[1] Different sources use different boundaries for the far infrared spectrum; for example, astronomers sometimes define far infrared as wavelengths between 25 µm and 350 µm.[2]
Visible light includes radiation with wavelengths between 400 nm and 700 nm, meaning that far infrared photons have less energy than visible light photons.[3]
Contents
1Applications
1.1Astronomy
1.2Longwave infrared heaters
1.3Human body detection
1.4Therapeutic modality
2References
3External links
Applications
Astronomy
Main article: Far-infrared astronomy
Due to black-body radiation, objects with temperatures between about 5 K and 340 K will emit radiation in the far infrared range according to Wien's displacement law. This property is sometimes used to observe interstellar gases where new stars are often formed.
For example, the center of the Milky Way Galaxy is very bright in far infrared images because the dense concentration of stars there heats the surrounding dust and causes it to emit radiation in this part of the spectrum. Disregarding the center of our own galaxy, the brightest far infrared object in the sky is the galaxy M82, which radiates as much far infrared light from its central region as all of the stars in the Milky Way combined. This is due to the dust at the center of M82 being heated by an unknown source.[2]
Longwave infrared heaters
Main article: Infrared heater
As of 2015, recently developed electric or hydronic panel-based longwave infrared heaters are becoming more adopted.[4]
Human body detection
Some human proximity sensors use passive infrared sensing in the far infrared wavelength to detect both static[5] and/or moving human bodies.[6]
Therapeutic modality
The infrared radiation (IR) band covers the wavelength range of 700 nm – 1 mm, frequency range of 430 THz – 300 GHz, and photon energy range of 1.24 meV – 1.7 eV. Far-infrared radiation (FIR) is found on the wavelength spectrum at 15–1000 µm with a frequency range of 0.3–20 THz, and photon energy range of 1.2–83 meV. In these IR radiation bands, researchers have noted that the far-infrared radiation band "transfers energy purely in the form of heat which can be perceived by the thermoreceptors in human skin as radiant heat."[7] They report that this radiant heat can penetrate up to 1.5 inches (almost 4 cm) beneath the skin. Biomedical researchers have experimented with the use of FIR emitting ceramics which are embedded into various fibers and woven into the fabric of garments. These researchers noted in subjects a "delay" in the "onset of fatigue induced by muscle contractions."[8] They propose that this ceramic-emitted FIR (cFIR) has the potential to promote cell repair.
References
^Byrnes, James (2009). Unexploded Ordnance Detection and Mitigation. Springer. pp. 21–22. ISBN 978-1-4020-9252-7.
^ ab"Near, Mid and Far-Infrared". Caltech Infrared Processing and Analysis Center. Archived from the original on 2012-05-29. Retrieved 2013-01-28.
^Gregory Hallock Smith (2006), Camera lenses: from box camera to digital, SPIE Press, p. 4, ISBN 978-0-8194-6093-6
^"Pyroelectric Detectors & Sensors for Far Infrared, FIR (5.0 µm-15 µm)". Excelitas. Excelitas. Retrieved 7 August 2015.
^Vatansever, Fatma and Michael R. Hamblin. Far infrared radiation (FIR): its biological effects and medical applications. Photonics Lasers Med. 2012 Nov 1; 4: 255–266.
^Leung TK, Lee CM, Tsai SY, Chen YC, Chao JS. A pilot study of ceramic powder far-infrared ray irradiation (cFIR) on physiology: observation of cell cultures and amphibian skeletal muscle. Chin J Physiol. 2011;54(4):247–54.
External links
Far infrared radiation (FIR): its biological effects and medical applications
Library resources about Far infrared
Resources in your library
Resources in other libraries
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