Principle of infrared:
Infrared (Infrared) is an electromagnetic wave with a wavelength between microwaves and visible light, with a wavelength between 1mm and 760 nanometers (nm), a non-visible light that is longer than red light.
Beyond absolute zero (-273.15 ℃) of the material can produce infrared. Modern physics calls them heat rays. Medical infrared can be divided into two categories: near infrared and far infrared. Containing thermal energy, the sun's heat is transmitted to the earth mainly through infrared rays.
Expanded Information:
Partitioning of the Infrared Spectrum:
The Infrared Spectrum is usually divided into three regions: the near-infrared region (0.75~2.5μm), mid-infrared region (2.5~25μm) and far-infrared region (25~300μm). Generally speaking, the near-infrared spectrum is generated by the doubling and combining frequencies of molecules; the mid-infrared spectrum belongs to the fundamental frequency vibration spectra of molecules; and the far-infrared spectrum belongs to the rotation spectra of molecules and the vibration spectra of certain groups.
Because the majority of organic and inorganic fundamental frequency absorption bands appear in the mid-infrared region, so the mid-infrared region is the most research and application of the region, the most accumulated information, the most mature instrumentation technology. The infrared spectrum is usually referred to as the mid-infrared spectrum.
Baidu Encyclopedia - Infrared