Infrared Rays (Meaning and Explanation)

We explain what infrared rays are, their types, history and characteristics. Also, its uses and main applications.

What are infrared rays?

Infrared radiation, popularly known as infrared rays, is a form of radiation that is part of the electromagnetic spectrum but it has a shorter wavelength than visible light (although longer than microwaves). These are electromagnetic waves whose wavelengths are between 0.7 and 1000 micrometers.

Since it is not part of the visible spectrum, our eyes are unable to perceive infrared radiation although we can detect it as a sensation of heat on the skin, for example, when we are exposed to the sun's radiation.

Furthermore, any type of matter that has a temperature higher than 0 degrees Kelvin (that is, -273.15 degrees Celsius, the so-called “absolute zero”) emits a certain level of radiation of this type. In fact, living beings emit a significant amount of infrared radiation due to our body heat.

On the other hand, depending on its location within the wavelength range, infrared rays may be of three types:

Near infrared. They are between 0.78 and 2.5 micrometers (it is the closest range to the visible spectrum).
Mid infrared. They are between 2.5 and 50 micrometers.
Far infrared. They are between 50 and 1000 micrometers.

Infrared rays have an important presence in nature. In addition, they have various applications in industry.

Characteristics of infrared rays

The characteristics of infrared radiation are the following:

They are a form of electromagnetic radiation that is outside the visible spectrum (we cannot see it with the naked eye).
Their wavelengths vary between 0.7 and 1000 micrometers and their frequency values are between 3 x 10¹¹ and the 3.84 x 10¹⁴
It is emitted by all bodies whose temperature is above absolute zero, in particular, by living beings, and is perceived as a form of surface heat.

History of infrared rays

The existence of infrared radiation was discovered at the beginning of the 19th century by the British-German musician and astronomer William Herschel (1738-1822), also discoverer of the planet Uranus.

Herschel used a mercury thermometer to measure the temperature of light in the visible spectrum, emitted through an optical prism. Thus he discovered that The values were higher towards the red side of the spectrum and that, even when he left it (that is, when he went beyond the visible red), the recorded heat continued to increase. This led him to conclude that he was in the presence of a form of invisible light, which he called “caloric rays.”

This experiment was replicated in the first bolometers (devices for measuring electromagnetic radiation) with which the infrared spectrum began to be studied, measuring the temperature values of light.

Uses of infrared rays

infrared rays temperature thermometer — Non-contact temperature control uses infrared rays.

Infrared radiation today has numerous human applications:

Night vision equipment. Using infrared light detectors, optical devices are manufactured that translate it into the visible spectrum, and allow us to “see” in the dark, guided by the heat emitted by objects. These implements are widely used in the war industry.
remote controls. The use of infrared emitters is common in remote controls and other teledevices, which would otherwise have to rely on radio waves and generate “ambient noise” for other more important forms of data transmission, such as Wi-Fi.
Infrared digital transmission. This type of data transmission technology (between computers or between computers and their nearby peripherals) uses infrared signals to transmit data over short distances.
Spectroscopic study in astronomy. By measuring infrared radiation from the atmosphere of cold stars, astronomers are able to study the chemical elements present in them. These rays are also used to study molecular clouds in space.
Surveillance and security. Measuring temperature levels in a closed environment allows new forms of surveillance and security, such as that applied in airports during pandemic periods, to detect abnormal temperature levels in a mass of moving people.