Kinds of Infrared
- The electromagnetic spectrum contains types of radiation that vary over a range of wavelengths. At one extreme are radio waves, which have wavelengths measured in hundreds of meters. On the other extreme are X-rays and gamma rays, which are measured in units of one billionth of a meter and are much higher in energy. IR radiation is found somewhere in the middle. It occupies the wavelength range with energy just slightly below the visible portion of the spectrum. IR radiation can heat up matter that it contacts and is produced by hot objects.
- The near infrared, or NIR, region of the EM spectrum is in the wavelength range of one to five microns, or one millionth of a meter. It is the closest to visible light in energy and wavelength, although it is still invisible to the human eye. NIR is absorbed by matter but does not result in much heating. However, it has some useful applications. It works well to carry information through fiber optics and is also used by labs in an form of instrumental chemical analysis. It is radiated by some stars such as red giants and can be useful in astronomy.
- The mid-infrared region, or MIR, spans approximately five to 50 microns in wavelength, and is further from the visible portion of light as compared to NIR. The human body emits IR light in this region, and IR cameras are sometimes made to capture MIR radiation. MIR is also used in chemical analysis to evaluate unknown chemical samples by their characteristic absorption patterns. Astronomers also utilize MIR to view cooler objects, such as planets and asteroids.
- The IR region furthest from the visible is aptly named far infrared, or FIR. It is located in the 50 to 350 wavelength region, and has the lowest energy of the IR section of the spectrum. FIR is generated by fires and other hot objects, and produces a sensation of heat when absorbed by the body. In astronomy, relatively cold matter, such as gas and dust clouds, become visible through their MIR emissions.
