<Ul> <Li> Far - infrared, from 300 GHz to 30 THz (1 mm--10 μm). The lower part of this range may also be called microwaves or terahertz waves . This radiation is typically absorbed by so - called rotational modes in gas - phase molecules, by molecular motions in liquids, and by phonons in solids . The water in Earth's atmosphere absorbs so strongly in this range that it renders the atmosphere in effect opaque . However, there are certain wavelength ranges ("windows") within the opaque range that allow partial transmission, and can be used for astronomy . The wavelength range from approximately 200 μm up to a few mm is often referred to as "sub-millimeter" in astronomy, reserving far infrared for wavelengths below 200 μm . </Li> <Li> Mid-infrared, from 30 to 120 THz (10--2.5 μm). Hot objects (black - body radiators) can radiate strongly in this range, and human skin at normal body temperature radiates strongly at the lower end of this region . This radiation is absorbed by molecular vibrations, where the different atoms in a molecule vibrate around their equilibrium positions . This range is sometimes called the fingerprint region, since the mid-infrared absorption spectrum of a compound is very specific for that compound . </Li> <Li> Near - infrared, from 120 to 400 THz (2,500--750 nm). Physical processes that are relevant for this range are similar to those for visible light . The highest frequences in this region can be detected directly by some types of photographic film, and by many types of solid state image sensors for infrared photography and videography . </Li> </Ul> <Li> Far - infrared, from 300 GHz to 30 THz (1 mm--10 μm). The lower part of this range may also be called microwaves or terahertz waves . This radiation is typically absorbed by so - called rotational modes in gas - phase molecules, by molecular motions in liquids, and by phonons in solids . The water in Earth's atmosphere absorbs so strongly in this range that it renders the atmosphere in effect opaque . However, there are certain wavelength ranges ("windows") within the opaque range that allow partial transmission, and can be used for astronomy . The wavelength range from approximately 200 μm up to a few mm is often referred to as "sub-millimeter" in astronomy, reserving far infrared for wavelengths below 200 μm . </Li> <Li> Mid-infrared, from 30 to 120 THz (10--2.5 μm). Hot objects (black - body radiators) can radiate strongly in this range, and human skin at normal body temperature radiates strongly at the lower end of this region . This radiation is absorbed by molecular vibrations, where the different atoms in a molecule vibrate around their equilibrium positions . This range is sometimes called the fingerprint region, since the mid-infrared absorption spectrum of a compound is very specific for that compound . </Li> <Li> Near - infrared, from 120 to 400 THz (2,500--750 nm). Physical processes that are relevant for this range are similar to those for visible light . The highest frequences in this region can be detected directly by some types of photographic film, and by many types of solid state image sensors for infrared photography and videography . </Li>

Light with a wavelength of 1500 nm is in what region of the electromagnetic spectrum