What is infrared radiation?

The infrared radiationalso called infrared light and often abbreviated with the acronym TO GOfrom the English Infrared Radiation, is one of the types of radiation that exist within the electromagnetic spectrum.

Like all radiation, infrared radiation transports radiant energy and behaves both as an electromagnetic wave and as a particle (photons).

The wavelength of infrared radiation occupies the range that goes from the 700nm (430 THz frequency) up to 1mm (300GHz).

It sits just above visible light (400-700nm), making it invisible to the human eye by definition. However, infrared radiation up to 1050 nm can be detected by the human eye under very specific conditions.

From the upper limit of infrared radiation (1 mm) microwaves begin.

Parts of the electromagnetic spectrum
Parts of the electromagnetic spectrum

infrared regions

Infrared radiation covers the range of wavelengths 700nm – 1mmbut it is usually divided into smaller regions for study and applications.

There are multiple subdivisions of infrared, generally with three main regions: near-infrared, mid-infrared, and far-infrared.

The limits of each of these regions may vary according to different sources and standards bodies.

Frequently used infrared regions

  • Near Infrared (NIR, IR-A DIN): 0.75–1.4 µm
  • Short Wave Infrared (SWIR, IR-B DIN): 1.4–3 µm
  • Medium Wave Infrared (MWIR, IR-C DIN, MidIR, IIR): 3–8 µm
  • Long Wave Infrared (LWIR, IR-C DIN): 8–15 µm
  • Far Infrared (FIR): 15–1000 µm

Infrared regions according to ISO 20473

  • Near Infrared (NIR): 0.78–3 µm
  • Mid Infrared (MIR): 3–50 µm
  • Far Infrared (FIR): 50–1000 µm

Infrared regions CIE (International Commission on Illumination)

  • GONNA: 700nm–1400nm (0.7µm–1.4µm)
  • IR-B: 1400nm–3000nm (1.4µm–3µm)
  • IR-C: 3000nm–1mm (3µm–1000µm)

Typical divisions in astronomy

  • Near Infrared (NIR): (0.7–1) up to 5 µm
  • Mid Infrared (MIR): 5 to (25–40) µm
  • Far Infrared (FIR): (25–40) to (50–1000) µm

These infrared divisions used in astronomy vary depending on the publication consulted, although the most common in astronomy is to assign capital letters to different ranges of the electromagnetic spectrum depending on the filter used for observation and measurement.

The letters I, J, H, and K cover most of the near infrared, while L, M, N, and Q cover most of the mid-infrared.

infrared radiation and heat

The infrared radiation was discovered in 1800 by astronomer William Herschelafter detecting a type of invisible radiation of lower energy than red light through its effects on a thermometer.

It was later discovered that most of the thermal radiation emitted by objects with a temperature close to room temperature is infrared radiation, so infrared radiation is commonly identified as "thermal radiation«.

Infrared radiation is emitted or absorbed by molecules together with changes in their vibrational and rotational movements, which translates into changes in temperature, although this effect can be caused by radiation of any wavelength.

Infrared radiation accounts for up to 49% of solar radiation. The rest of solar radiation is visible light and a small fraction is ultraviolet radiation.

Despite this clear relationship with the heat we receive from the Sun, it is important to be clear that thermal radiation can be produced at any wavelength. For example, an incandescent object emits radiation in the range of visible light.


Infrared radiation has multiple and varied applications at the industrial, scientific, medical, military and domestic levels. Some of these applications are summarized in the following list:

  • Night vision: Infrared radiation is used by night vision devices, detecting photons from ambient light and transforming them into amplified electrical signals.
  • thermography: Allows you to determine the temperature of objects from a distance.
  • hyperspectral image: is an image in which each pixel contains a continuous spectrum over a wide spectral range.
  • Heating: Infrared radiation can be used as a heat source, for example to remove ice from aircraft wings, in infrared saunas, for cooking and heating food, or in numerous industrial applications.
  • Communications: Infrared data transmission has been widely used in connections between computers and peripherals, in remote controls and remote controls. Infrared lasers are also used in fiber optic communication systems.
  • Spectroscopy: Infrared vibrational spectroscopy is a technique that allows the identification of molecules through the analysis of atomic bonds and their vibration. It is mainly used for the study of organic molecules.
  • Meteorology and climatology: meteorological satellites are capable of producing thermal and infrared images whose study allows us to deduce the size and type of clouds, calculate the temperature of ocean surface water, among others, which allows us to make meteorological predictions.
  • Astronomy: The study of space with infrared telescopes allows us to observe the interior of clouds of gas and dust, which are usually cold and dark, by observing the heat radiated by the stars inside. Infrared astronomy also makes it possible to observe highly redshifted objects whose formation dates back to the very beginning of the Universe itself.
  • Analysis and conservation of works of art:Infrared reflectography is a technique applied to paintings to visualize lower layers, for example the drawings that painters made as a guide for painting.
  • Photobiomodulation: Near-infrared radiation is used to treat chemotherapy-induced mouth ulcers and to promote wound healing. Among the possible mechanisms is the activation of the enzyme cytochrome C oxidase.
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