Far infrared

Diagram of part of the electromagnetic spectrum

Far infrared (FIR) or long wave refers to a specific range within the infrared spectrum of electromagnetic radiation. It encompasses radiation with wavelengths ranging from 15 μm (micrometers) to 1 mm, which corresponds to a frequency range of approximately 20 THz to 300 GHz. This places far infrared radiation within the CIE IR-B and IR-C bands.[1] The longer wavelengths of the FIR spectrum overlap with a range known as terahertz radiation.[2] Different sources may use different boundaries to define the far infrared range. For instance, astronomers often define it as wavelengths between 25 μm and 350 μm.[3] Infrared photons possess significantly lower energy than photons in the visible light spectrum, with tens to hundreds of times less energy.[4]

  1. ^ Byrnes, James (2009). Unexploded Ordnance Detection and Mitigation. Springer. pp. 21–22. ISBN 978-1-4020-9252-7.
  2. ^ Glagoleva-Arkadiewa, A. (1924). "Short electromagnetic waves of wave-length up to 82 Microns". Nature. 2844 (113): 640. Bibcode:1924Natur.113..640G. doi:10.1038/113640a0.
  3. ^ "Near, mid and far-infrared". Caltech Infrared Processing and Analysis Center. California Institute of Technology. Archived from the original on 2012-05-29. Retrieved 2013-01-28.
  4. ^ Gregory Hallock Smith (2006), Camera lenses: from box camera to digital, SPIE Press, p. 4, ISBN 978-0-8194-6093-6