Far infrared

<p>Far infrared (FIR) or long wave refers to a specific range within the <a href="/facts/Infrared_spectrum/44XdJNcc">infrared spectrum</a> of <a href="/facts/Electromagnetic_radiation/Ynx7ujCW">electromagnetic radiation</a>. It encompasses radiation with wavelengths ranging from 15 μm (<a href="/facts/Micrometre/7eDFxD2L">micrometers</a>) to 1 mm, which corresponds to a frequency range of approximately 20 THz to 300 GHz. This places far <a href="/facts/Infrared_radiation/44XdJNcc">infrared radiation</a> within the CIE IR-B and IR-C bands. The longer wavelengths of the FIR spectrum overlap with a range known as <a href="/facts/Terahertz_radiation/729QecPK">terahertz radiation</a>. 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. Infrared <a href="/facts/Photon/mFNhAEzA">photons</a> possess significantly lower energy than photons in the <a href="/facts/Visible_light_spectrum/frPBh8o5">visible light spectrum</a>, with tens to hundreds of times less energy.
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Far infrared open-in-new

Far infrared