When was the last time you thought about what happens when you turn on your television? You might not realize it, but that little red dot is actually sending electromagnetic waves to a processor that handles all of your commands.
You won’t see it, but infrared light is used for everything from toasting your bread in the morning to searching for people in the dark.
Continue reading for everything you need to know about infrared radiation. Let’s jump in!
What is Infrared Light?
Infrared (IR) radiation is a portion of the electromagnetic spectrum that has longer wavelengths than the visible spectrum. While it’s located next to the visible red light on the spectrum, it is invisible to the human eye. However, you’ve likely experienced it before; IR is commonly associated with the heat released from objects.
The electromagnetic spectrum is typically measured in three different metrics, depending on which one is easiest to read. Infrared is often measured in wavelength, which uses meters as its unit. While there’s no hard line that defines the length of IR waves, they generally measure between .7µm (near-IR) and 1000µm (far-IR).
Infrared radiation emits from any object that produces heat and has a variety of uses. Its most common application includes thermal imaging, in which a special IR tool senses wavelengths and paints a picture based on their different sizes. Other uses for IR include remote controls and astronomy.
While some infrared penetrates the atmosphere, much of it is dissipated in the stratosphere. Because of its significance in astronomy, researchers use orbital satellites to observe the universe in this wavelength range.
Infrared Light: An Exact Definition
The International Commission of Non-Ionizing Radiation Protection (ICNIRP) is a non-profit organization that aims to protect people from the harmful effects of low-frequency radiation. The organization has worked with international health committees for nearly 50 years and has helped establish much of what we know about non-ionizing radiation.
According to the ICNIRP, Infrared light, “also known as thermal radiation, is that band in the electromagnetic radiation spectrum with wavelengths above red visible light between 780 nanometers (nm) and 1 micrometer (mm).”
IR is categorized as:
- IR-A, or near-IR (780nm – 1.4µm)
- IR-B, or mid-IR (1.4µm – 3µm)
- IR-C, or far-IR (3µm – 1mm)
Where Does Infrared Light Come From?
Cool Celestial Bodies
Infrared radiation represents the cooler edge of visible light; as its wavelengths are less frequent than ultraviolet, objects that lean toward orange, red, and infrared produce less heat.
A great example of an object releasing IR waves is our sun. According to the UCAR COMET program, the sun releases about 49% of its radiation as infrared (followed by 43% as visible light). This suggests that our sun is relatively cool compared to others.
NASA scientists use this information to search for low-energy celestial bodies such as planets, nebulae, and other cool stars. Because of their longer waves, infrared penetrates dense space dust. With IR instruments, researchers can discover objects that would otherwise be invisible.
In the same sense as cool stars, many of the heat sources found on Earth exude infrared radiation. Some of the more prevalent examples of Earth-based IR sources include lava flows and forest fires. Firefighters can use infrared detectors on smoke to discover the location of burns in the forest before they spread out of control.
Any object that produces heat at a temperature of minus 450 degrees Fahrenheit or above emits infrared radiation. As such, the human body also produces a significant amount of IR. We can use infrared cameras to image our bodies in the dark, such as with night vision goggles.
How Do You Create Infrared Light?
Infrared wavelengths emit from objects that release heat. In that regard, most heat is created through friction. Friction occurs when two objects are pressed together and moved over each other. The more resistance that the objects encounter, the more friction.
It doesn’t take much friction to create heat, but it would take a considerable amount to emit near-infrared waves. Most heaters that operate at this wavelength produce temperatures of over 3,200 degrees Fahrenheit. Beyond this, heat sources can start to produce visible light.
Who Discovered Infrared Light?
In 1794, William Herschel discovered a sense of warmth while observing the sun in low-light areas. It was curious that areas void of light could emit more heat than areas on the visible light spectrum. With his understanding of the sun, Herschel reasoned that the emitted energy might parallel the emitted heat.
In 1800, Herschel built a spectroradiometer, which could measure the level of emitted energy at different wavelengths. The spectroradiometer, or spectrometer, is a prism to absorb sunlight and disperses the colors where Herschel could measure each portion’s heat. He used a cardboard piece with a slit to focus on each section and used a thermometer to check the temperature. He discovered that yellow and green produce more radiant power than red or violet.
However, the heat released from each color did not follow the same trend as radiant energy; instead of peaking around yellow and green, the heat continued to increase beyond red. This caused Herschel to believe that heat wasn’t caused by the illumination, but instead by waves. He named this wave beyond red “invisible light.”
What are the Applications of Infrared Light?
When you unscrew an incandescent lightbulb that’s been on for a time, you might feel intense heat. While these lights release visible light, most of their energy emits in the form of infrared radiation. The same is true with other household heat sources such as heat lamps and toasters.
However, not every IR use emits heat; when you turn on your television with your remote control, the device sends far-IR wavelengths to communicate. The wavelengths cause the microprocessor within the television to react, allowing you to change the channel, lower the volume, or turn it off altogether from wherever the two devices can see each other.
On a more commercial scale, infrared is used to image low-temperature objects that would otherwise be hidden. This is typically used in night vision goggles, and they have electronic sensors that depict different IR wavelengths. While useful for seeing humans in the dark, researchers also use it to monitor chemical reactions in materials as they’re exposed to different elements.
Like night vision goggles, astronomers use spectrometers to view low-energy objects in space. In particular, researchers observe mid-infrared to discover exoplanets that don’t produce as much heat as stars or galaxies. NASA scientists are searching for planets in nearby galaxies that have similar features as Earth to find signs of life.
Examples of Infrared Light in the Real World
Medical Infrared Thermography
Oncologists use infrared thermography to discover possible patterns of abnormal cell development. This process uses an infrared camera to study areas of concern; because cancer cells produce more heat than usual, the infrared camera can reveal where the treatment needs to focus. IR thermography is non-invasive and produces no radiation, making it a safe method of cancer discovery.
Military Infrared Jamming
In 1990, the U.S. military found contention from Iraq’s infrared-homing missiles during the Gulf War. As a response, the military developed infrared countermeasures; in addition to flares and false heat targets, the Air Force built jammers to disrupt the timing pattern in heat seekers. This found great success, saving up to 80% of the military’s air losses.
James Webb Space Telescope
Following the legacy of the Hubble Space Telescope, NASA launched the James Webb Telescope in December 2021 to observe the universe in near- and mid-infrared. The massive observatory uses three IR cameras and spectrometers to view distant objects through space dust.
Most recently, the JWST viewed through the Tarantula Nebula, one of the largest stellar nurseries in the known universe, to discover characteristics of the period in which stars were produced at their peak.
Up Next: More on Infrared Light
While we cannot see it, infrared light plays a significant role in our everyday lives. From the heat in our toasters to thermal imaging in cancer studies, we rely on IR technology when temperature is involved. For more on wavelengths and how we use the electromagnetic spectrum, check out the articles below.
- What are EMFs (Electric and Magnetic Fields)? Are They Safe?
- Bluetooth vs. Infrared: What’s the Difference?
- Top 10 Largest Space Telescopes
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