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Infrared Radiation – Definition, Characteristics, Uses

Aug 13, 2022

Infrared Radiation

We only view a small section of the electromagnetic spectrum daily in visible light. All forms of radiation, from the radio waves used for telecommunications to the X-rays and MRI used in hospitals, are included in the electromagnetic spectrum. Infrared radiation in the electromagnetic spectrum is also classified by wavelength. Short wavelength radiation like X-rays, gamma, and ultraviolet rays are high-intensity radiation that can potentially harm the human body.

Radio, and microwaves, are examples of longer infrared radiation wavelengths that are less hazardous to the human body. The article goes into great detail about infrared radiation and its characteristics and applications. Humans may detect infrared radiation as heat even though it cannot be seen. Place your hand close to a hot microwave to feel infrared radiation!


Define Infrared Radiation: What is an Infrared Radiation?

Infrared radiation definition: It is a sort of radiant energy (often known as infrared light) that we experience as heat but is not visible to human eyes. The fire and sun are two of the most prominent infrared radiation examples. However, all bodies in the cosmos release some of it.

Infrared radiation is a spectrum of frequencies generated where atoms acquire and then release energy. Electromagnetic radiation includes all types of radiation ranked by frequency from highest to lowest, including gamma, X-rays, visible, ultraviolet, infrared, radio waves, and microwave. When combined, these radiations constitute the electromagnetic spectrum.


So what is infrared radiation? It is a form of electromagnetic radiation (EMR), which is usually longer than the visible light wavelength. Consequently, it is not visible to the human eye, in contrast to occasionally visible infrared light from specially rectifier diodes with wavelengths up to 1050 nanometers (nm).

Infrared light is thought to extend from the visible spectrum’s supposed red edge between 700 nanometers to one millimeter. Most of the thermal radiation released by items near room temperature is infrared. Like all electromagnetic radiation, infrared radiation transmits radiant energy and functions as both a photon and a wave, a quantum particle. Infrared is typically split into five categories depending on their wavelength and frequency:

  • Near-infrared
  • Short wavelength infrared
  • Mid wavelength infrared
  • Long wavelength infrared
  • Far infrared

Characteristics of Infrared Radiation Regions

Near Infrared

  • The infrared wavelength is between 0.75 – 1.4 micrometers.
  • It is employed in studying materials, fibre optic communication, and medicine.

Short Wavelength Infrared

  • The infrared wavelength is between 1.4 – 3 micrometers.
  • They are used by both defence and telecommunications applications industries.

Medium Wavelength Infrared

  • The infrared wavelength is between 3 – 8 micrometers.
  • Used by both astronomy and the chemical processing industries.

Long Wavelength Infrared

  • The infrared wavelength is between 8 – 15 micrometers.
  • Long infrared radiation wavelengths can be used for optical fiber communications and astronomical telescopes (equipment).

Far Infrared

  • The infrared radiation wavelength is between 15 – 1000 micrometers.
  • It is mostly employed in cancer therapy.

Who discovered Infrared Radiation?

NASA claims that in 1800, British astronomer William Herschel discovered infrared light. In an experiment, he arranged a thermometer in the path of light inside every color of the visible light spectrum to determine the temperature difference between the colors. As moving from blue to red, he noticed a temperature rise, and just beyond the red, he discovered an even warmer temperature reading at the end of the visible light spectrum.

The term “infrared” refers to electromagnetic waves whose frequencies are just below that of visible red light and above that of microwaves. As per the California Institute of Technology (Caltech), Infrared radiation waves are longer than visible light waves. According to NASA statistical data, IR wavelengths are thought to be between 1,000 micrometers (m) and 760 nanometers (2.9921 inches). However, these figures are not conclusive. IR frequencies vary from approximately 300 gigahertz (GHz) to approximately 400 terahertz (THz).


Infrared Radiation Wavelength

As previously known, the visible light spectrum’s red limit is between 700 nm and 1 mm, which is the wavelength range of infrared radiation. However, the following is how bands are categorized depending on the wavelength range between 1µm and 50µm:

  • Band I, or short infrared wave, spans the wavelength range of 1µm to 3µm.
  • Band II, or middle infrared wave, travels the wavelength range of 3µm to 5µm.
  • Band III, or long infrared wave, spans the wavelength range of 8µm to 14µm.

Infrared Waves: Properties

Infrared sun radiation is a major energy source that reaches the Earth. The climate of the Earth is significantly influenced by the ratio of infrared radiation that is absorbed and released. The following are properties of infrared waves described below.


Transverse Waves

Per Serway’s College Physics, an infrared wave is described as a transverse wave, implying that its displacement is at a right angle to the wave’s direction of travel.


Infrared rays have distinctive wavelengths that are often measured in microns. One millionth of a meter is referred to as a micron. A typical infrared wave has a wavelength of 0.7 microns. Infrared waves have a maximum wavelength of 350 microns. As per research, the maximum wavelength of any infrared wave is 1000 microns.



Infrared waves move at a speed of 299,792,458 m.s-1.

Wave or Particle?

As per the quantum theory, infrared waves can exist simultaneously as a wave and particle.


Reflection and Absorption

The type of substance that infrared radiation is directed at determines how those waves will be absorbed and reflected. Infrared radiation is absorbed by substances like carbon dioxide, ozone, and water vapour. Materials like snow and aluminium foil reflect infrared radiation.

Interfering and Refracting

Refraction is a wave feature that causes infrared waves to slightly alter direction when they go from one medium to another. The Earth’s atmosphere exhibits the infrared wave’s refraction feature. When two infrared radiation of the same wavelength interacts, they will interfere.

Thermal Properties

Because infrared rays have thermal qualities, they can produce heat. When nitrogen or oxygen molecules are exposed to infrared radiation, the energy from the radiation causes the molecules to travel more quickly. Therefore, we can state that infrared radiation increases materials’ temperature, enabling it to be employed as a heat source.

Did You Know?

One of the three methods by which heat is transferred—the other two being conduction and convection—is by infrared radiation. Thus, what is infrared radiation? Or how to define infrared radiation? It is the radiation produced by anything with a temperature greater than about 5 degrees Kelvin (minus 268 degrees Celsius or minus 450 degrees Fahrenheit). As per the University of Tennessee, the sun emits half of its total energy as infrared, and a large portion of the star’s light waves is absorbed and then re-emitted as infrared.

Uses of Infrared Waves

The following are some applications for infrared waves:

Heat Source

Infrared radiation is used as a heat source in two distinct industries:

Infrared radiation is used as a heating source in the medical field. Rheumatoid arthritis and high blood pressure are both treated using infrared saunas. In physiotherapy, infrared radiation is considered one of the safest options.

Industries focusing on industrial processes, such as coating curing, plastic welding, and contact heating, employ infrared heaters instead of convection ovens and contact heaters.

Application of Cosmetology

Infrared radiation is frequently utilized in the cosmetic industry to cure skin damage, prevent the severity of dandruff and blackheads, and heal wrinkles. Infrared radiations are employed because they can pass within the skin up to 3–4 mm. They also heat up and relax the skin, enhancing blood flow and supplying the skin with nutrients and oxygen continuously.


Astronomers employ optical tools such as solid-state digital sensors, mirrors, and lenses to investigate things from space. An infrared telescope is used to get pictures from these optical instruments.

Massage Treatment

The skin is treated by infrared rays, which help relax the muscles. Infrared rays are preferred because they penetrate the skin more effectively.

Infrared Radiation Photography

Infrared photography employs infrared filters to take photos. This photography is carried out for items located in the near-infrared light spectrum. Most digital cameras use infrared blockers, which causes the near-infrared to appear as a purple-white colour in the final photo.

Infrared Communication

Infrared light is frequently used to transmit data in short-range communication. Infrared light-emitting diodes generate infrared radiation and are concentrated into a narrow beam with a plastic lens to encode the data. A photodiode is positioned at the receiver end to transform infrared radiation into an electric charge.

Examples of Infrared Radiation 

Long-wave infrared radiation (LWIR) 

  • Long-wave infrared radiation is used to convey the heat produced by fires and ignited charcoal. 

Short-wave infrared radiation (SWIR) 

  • Short-wave infrared radiation is emitted by most television remote controls. 


When an object is heated, it may emit infrared radiation from it. The object’s atoms and molecules begin to vibrate, emitting heat from infrared radiation. This infrared radiation is emitted by objects when their temperatures are insufficient to create visible light. Additionally, the creation of heat is not affected by the ambient temperature.

Frequently Asked Questions

1. What are the medical advantages of infrared radiation?

 Here are a few of infrared radiation’s therapeutic effects:

  • Used to minimize nose, ear, and throat inflammation.
  • Used as a tool for managing stress.
  • Decreases arthritic pain.
  • Facilitates easy functioning of the kidney.

2. How do we regularly come into contact with infrared radiation?

Infrared is radiant energy that we can only perceive as heat because it is not visible to the human eye. Infrared radiation is emitted at some level by every item in the cosmos. The most obvious infrared radiation examples include the sun and fire.

3. List some of the characteristics of infrared radiation.

 The infrared spectrum has the following characteristics:

  • The speed of all radiation, including infrared, is 299,792,458 meters per second.
  • Both a wave and a particle nature can coexist in infrared light.
  • Infrared radiation can be reflected or absorbed based on the material it encounters.
  • The thermal energy of particles is increased by infrared light.
Infrared Radiation


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