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30 Amazing Facts About Infrared Waves

Infrared waves are a type of electromagnetic radiation that is invisible to the human eye. Although we cannot see them, infrared waves play an important role in our everyday lives. From keeping us warm to enabling night vision technologies, infrared radiation has a wide range of applications that impact us on a regular basis.

In this blog post, we will explore 30 fascinating facts about infrared waves. We will learn about the discovery of infrared radiation, how it is generated, and some of its key properties. We will also look at some of the practical uses of infrared waves in science, technology, and even astronomy. Read on to learn things you may not know about the infrared part of the electromagnetic spectrum!

1.Discovery Of Infrared Rays

It may be hard to imagine, but infrared radiation remained undiscovered until about 200 years ago. The existence of infrared waves was first discovered in 1800 by astronomer Sir Frederick William Herschel. He was exploring different colored filters and their effect on heat from the sun. When he directed sunlight through a prism to create a rainbow spectrum, he found the highest temperature just beyond the red end of the visible spectrum. This is where he detected infrared radiation for the first time.

However, the term “infrared” did not come until later. In the 1840s, Macedonio Melloni coined the term “infrared” to describe these invisible heat rays beyond the red end of the visible spectrum. The prefix “infra” means “below” in Latin. So, infrared refers to radiation below the range of red light that humans can perceive. Melloni paved the way for more exploration and discovery of infrared radiation.

2. All Objects Emit Infrared Radiation

Infrared Radiation captured by a Cellphone, , via Wikimedia Commons.

Anything that gives off heat also emits infrared radiation. That means all objects with a temperature above absolute zero give off varying levels of infrared waves. The hotter an object gets, the more infrared waves it emits. A good example is the electric stove top in your kitchen. When you turn on a burner, it glows red because it becomes hot enough to also emit visible light. But it is also emitting higher levels of infrared radiation which we cannot see with the naked eye.

Even cold objects like ice cubes emit some infrared rays. The amount varies based on temperature. This is important because it enables infrared cameras and sensors to detect radiation coming off objects in a room. Night vision goggles pick up these infrared signals to identify living beings and other objects. Whether hot or cold, every object constantly gives off some level of infrared radiation. Without infrared waves, technologies like night vision would simply not work because there would be no signals to pick up!

3. Infrared Rays Have Longer Wavelengths

Infrared radiation sits between the visible light and microwave portions of the electromagnetic spectrum. It has longer wavelengths than visible light that humans can see. Infrared wavelengths range from about 700 nanometers to 1 millimeter. For comparison, visible light wavelengths range from roughly 400 to 700 nanometers.

The longer wavelengths of infrared rays are the key reason they are invisible to our eyes. Our human vision only picks up on the shorter wavelengths of visible light. Infrared wavelengths are too long for our biological vision to detect. However, we can feel infrared rays in the form of heat if the wavelengths are short enough. For instance, we feel the heat from a fireplace since those infrared waves have short enough wavelengths to be detected as heat on our skin.

Other portions of the infrared spectrum have such long wavelengths they do not create noticeable heat. For example, microwaves have infrared wavelengths ranging from 1 millimeter to 1 meter. We do not sense this radiation as heat. But it can still cook food because the waves interact with water molecules. So, wavelength determines if infrared will be felt as heat or simply pass through us undetected.

4.  Infrared Rays are Generated by Molecular Motion

Molecule models. , , via Wikimedia Commons

What actually causes objects to emit infrared radiation in the first place? The source of infrared waves is molecular motion. As molecules rapidly vibrate and rotate, they create infrared radiation as a byproduct. The faster molecules move within an object, the more infrared waves they will produce.

For example, increasing temperature speeds up molecular motion. As a stove element heats up, its molecules shake and twist faster and faster. This accelerated molecular activity releases a flood of infrared rays. The emission of infrared radiation then further heats up molecules that absorb the radiation. So molecular motion creates infrared rays, while also being accelerated by their absorption.

Besides temperature, other factors like molecular structure and bonding also affect molecular vibration and rotation. Larger molecules composed of many atoms tend to emit more infrared rays thanks to their complex structure. Thus, infrared spectroscopy is an important chemical analysis tool because infrared emission reveals details about a material’s molecular composition. Overall, infrared radiation arises from the natural motions within material at the molecular level.

5. Infrared Rays Transmit Heat

HEAT TREATMENT. , , via Wikimedia Commons

A key property of infrared radiation is its ability to transmit heat. When infrared light is absorbed by an object, it converts to heat. Shorter infrared wavelengths that we perceive as heat can warm our skin. But even longer wavelengths heat things up by exciting molecule motions deep below the skin surface.

This transmission of warmth by infrared radiation is what allows heat to travel through the vacuum of space. The sun delivers energy to Earth across millions of miles thanks to infrared radiation. A campfire or fireplace also heats nearby objects through the infrared waves flowing from the flames. Greenhouse gases like carbon dioxide absorb this infrared heat, leading to global warming through the greenhouse effect.

On a more short-term basis, infrared lamps use this principle to focus warmth on sore muscles or cold hands. The penetrating nature of infrared radiation makes it the perfect vehicle to transport heat from one location to another without physical contact. So, whether it is warming our planet or simply a chilled person, infrared waves have a unique ability to transmit thermal energy through the emptiness of space.

6.  Infrared Radiation Has Many Subdivisions

Within the broad infrared portion of the spectrum, there are actually several subcategories of infrared radiation.

So, infrared is not one homogeneous type of radiation. It spans a wide range of wavelengths from the edge of human vision out to the start of microwaves. Each subdivision has advantages. Near-infrared supports fiber optic transmission for internet and telecom. Mid-infrared is ideal for thermal imaging. Far-infrared alters molecule structures. And terahertz radiation enables security scanning.

Most infrared applications rely on a specific portion of infrared waves matched to the desired function. There is no one-size-fits-all infrared radiation. By tuning into the ideal wavelength range, infrared can provide amazing imaging, sensing, communication and material altering capabilities.

7. Infrared Rays are Divided into Spectral Bands

Spectral Bands , , via Wikimedia Commons.

Zooming in further, the infrared domain consists of a series of distinct spectral bands. Spectral bands are specific wavelength ranges where infrared radiation interacts strongly with molecules. There are three infrared spectral bands:

he mid-infrared band is the spectral sweet spot for thermal radiation beneficial for heat-seeking infrared cameras. On the other hand, the far-infrared band behaves more like radio waves that pass-through objects. Each band has prime “windows” where infrared interacts with matter in useful ways.

Think of it as listening to different radio stations. Tweaking the wavelength gives you completely different content. Infrared bands are like preset channels optimized for certain infrared properties. Most infrared devices are designed to detect or emit on specific spectral bands rather than the entire infrared range. Tuning into the ideal band for the job is the key to effectively harnessing infrared’s advantages.

8. Multiple Technologies Use Infrared Waves

From military gear to common household devices, infrared radiation plays a role in numerous technologies people rely on daily:

Night vision – Goggles, scopes, cameras detect infrared instead of visible light.

Thermal imaging – Scanners sense temperature variation from mid-infrared emissions.

Infrared spectroscopy – Studies interactions between matter and infrared rays.

Infrared heaters – Emit infrared radiation to warm people and objects.

Remote controls – Send signals to TVs and other devices using infrared LEDs.

Cooking appliances – Microwaves and infrared grills use infrared to heat food.

Optical fiber – Carries data on near-infrared wavelengths for telecommunications.

Astronomy – Captures infrared light from cool, faraway celestial objects.

The list goes on and on. Even the motion sensors that automatically activate sinks and public toilets rely on small infrared detectors. Infrared may not be visible, but it enables many everyday gadgets we take for granted simply by harnessing different portions of this invisible spectrum.

9. Infrared Photography Reveals the Invisible

Infrared light as recorded by a digital camera. , , via Wikimedia Commons

While standard cameras only capture visible wavelengths of light, infrared photography uses specialized film or sensors to reveal the world through infrared eyes. It offers a glimpse into the unseen details all around us.

In infrared photographs, green leaves appear white because they strongly reflect near-infrared rays. Blue skies look black since water vapor absorbs infrared. Synthetic fabrics glow brightly while natural wood or leather seem dark. It produces an eerie, alien-like rendering quite unlike normal human vision.

Infrared photography has scientific, artistic and security applications. Researchers use infrared to study plant health. Fine art photographers utilize infrared techniques to create dream-like landscapes and portraits. Police employ infrared to see suspects hiding in darkness. No extravagant filters or lens flare required!

Of course, anyone can get a taste of infrared simply by using a TV remote and camera phone. Point the remote at the camera and press buttons to see the otherwise invisible infrared LED flashing on through the lens. This rehearses the same principles used in multi-million-dollar infrared surveillance systems!

10. Water Vapor Strongly Absorbs Infrared

Something as intangible as humidity can actually have a noticeable impact on infrared waves. Water vapor in the atmosphere readily absorbs certain infrared wavelengths emitted from Earth’s surface. This prevents some infrared radiation from escaping our planet.

The reason has to do with infrared spectroscopy and absorption bands. Water exhibits absorption peaks precisely where Earth emits the bulk of its infrared radiation. This creates a natural phenomenon called the greenhouse effect. While beneficial in moderation for maintaining habitable temperatures, excessive greenhouse gas absorbs too much rising infrared radiation and traps excess heat.

Beyond the atmosphere, water also influences infrared in space. Night vision often does not work well when pointing at water surfaces because water rapidly soaks up infrared waves. That is also why infrared astronomy favors studying objects through “infrared windows” where the views are not obscured by water vapor between Earth and space. So, despite being invisible, atmospheric water substantially impacts the propagation of infrared radiation above and below the sky.

11. Infrared Radiation Can Cause Burns

Burns patient. , , via Wikimedia Commons

While infrared radiation seems harmless since we cannot see it, intense levels can actually damage skin and eyes. Prolonged exposure can produce burns due to the deep heating effects. For instance, glass blowers working near extremely hot furnaces experience infrared burns on their exposed skin even at a distance.

Welders are also at risk of infrared burns on the face and eyes when working under high-intensity radiation without proper eye protection. In rare cases, extremely intense pulses of infrared radiation have caused retinal damage. Safety standards limit the amount of human exposure to avoid infrared radiation hazards.

On the flip side, carefully controlled doses of infrared radiation have medical benefits. Infrared heating pads soothe sore muscles and arthritis aches. The FDA has even approved near-infrared light therapy for certain conditions like wounds and nerve pain. And of course, we all enjoy the infrared warmth from sunshine and campfires (in moderation). So infrared radiation can be helpful or harmful depending on the amount and means of exposure.

12. Greenhouse Gases Absorb Infrared

We have all heard about the warming effects of greenhouse gases like carbon dioxide, methane and water vapor. But what makes them “greenhouse” gases in the first place? It comes down to how they interact with infrared radiation through the greenhouse effect.

As Earth’s surface heats up from sunlight, it releases mid-infrared heat radiation back toward space. However, greenhouse gases in the atmosphere readily absorb this rising infrared radiation. The absorbed infrared converts to heat, warming the gases. This heat gets sent back down toward the surface rather than escaping into space.

Think of the greenhouse gases like a partial blanket for Earth. Just like a blanket trap your body heat to keep you warm, greenhouse gases trap infrared heat rising from the ground. This heat-trapping mechanism is essential to maintaining a habitable climate. But excessive greenhouse gas leads to over-absorption of infrared, preventing excess surface heat from radiating away. The result is global warming.

So the term “greenhouse gas” comes from the ability of certain gases to literally act like a greenhouse by absorbing infrared and preventing heat loss. Their molecular structure makes them inherently adept at catching rising infrared radiation.

13. Carbon Dioxide Strongly Absorbs Infrared

A container of liquid carbon dioxide. , , via Wikimedia Commons

Of all the greenhouse gases, carbon dioxide has a greenhouse effect on steroids. The double carbon-oxygen bonds in its molecular structure undergo vibrational and rotational motions that just happen to resonate at the same frequencies as infrared radiation emitted by Earth’s surface.

This makes carbon dioxide extremely “IR-active” – meaning it excels at interacting with and absorbing infrared photons. In particular, it absorbs infrared in two distinct absorption bands centered around 2.7 and 4.3 microns. These bands fall right in the mid-infrared wavelengths characteristic of blackbody radiation emitted by our planet.

Once carbon dioxide absorbs this rising infrared heat, it re-emits the radiation in all directions. Some returns back down toward the surface rather than escaping into space. More carbon dioxide means more absorption and radiation of infrared rays back down to induce warming.

While carbon dioxide is not the most potent greenhouse gas, it has an incredibly long lifetime in the atmosphere – up to thousands of years. As carbon dioxide accumulates from human emissions, its escalating atmospheric concentration makes it increasingly efficient at trapping infrared radiation and driving the enhanced greenhouse effect.

14.  Some Materials Block or Reflect Infrared

While many materials readily absorb infrared, other substances interact differently with these invisible rays. Some are essentially transparent to certain infrared wavelengths. And other materials actually reflect rather than soak up the radiation.

For example, zinc sulfide and calcium fluoride crystals transmit mid- and far-infrared with very little loss. This makes them ideal materials for infrared windows that allow infrared detectors and sensors to operate. On the other hand, smooth metals like aluminum and gold reflect back a substantial portion of incident infrared radiation rather than absorbing it.

Special coatings can enhance infrared reflection further. That’s why emergency blankets made of lightweight metallic Mylar sheets help retain body heat. The crinkly blankets reflect your own rising infrared radiation rather than allowing it to dissipate away. Similar coatings on vehicle exhaust pipes and even spacesuits help control heat management by directed infrared radiation.

So while many natural materials interact strongly with infrared, some have been engineered to deliberately reduce such interactions. Allowing infrared to freely pass through or bounce away is just as important as absorbing it for applications like imaging, thermoregulation, or minimizing trace detection.

15.  Infrared Has Communications Applications

WDET FM Transmitter. , , via Wikimedia Commons

With the right transmitters and receivers, infrared light can carry information just like visible light, radio waves or other wireless signals. Today, infrared is widely used for short-range data communication. Remote controls practically all operate on infrared frequencies, enabling your clicker to “talk” to the TV without any wires.

Infrared communications have some advantages over radio waves for certain applications. Infrared does not penetrate walls as easily, so it can be used for secure indoor applications without broadcasting beyond the room. Infrared sources like LEDs tend to use less power than radio transmitters. And infrared has hundreds of terahertz of available bandwidth suitable for high-speed, short-distance communication.

Infrared data transmission finds uses in personal area networks, smartphones, laptops and other devices. Infrared ports in old PDAs used to exchange contact and calendar data by simply pointing two devices at each other. While less common today, infrared still has niche applications where localized, private communication links are desirable. The same infrared rays that provide night vision or heat up food can also transmit invisible messages right under our noses.

16. All Humans Constantly Emit Infrared

It turns out you don’t need special equipment to be an infrared source. The human body naturally emits infrared radiation as a function of our warm-blooded metabolism. Everything with a temperature above absolute zero emits infrared corresponding to that warmth. But living organisms in particular give off significant levels in the mid-infrared band.

Human skin at room temperature radiates at wavelengths centered around 9.4 microns. Water is a decent infrared absorber at many bands, and the human body is mostly water. Yet the water does not absorb all our internally-generated infrared because of a transparency window from about 8 to 14 microns. Some radiation in this band can escape through the water molecules.

With the right infrared camera, it is possible to visualize this infrared bio-glow emanating from a human subject. This passive infrared radiation is what enables night vision goggles to spot people in the dark based on their heat signature. Unfortunately for hiding criminals, there is no way for a warm human body to suppress the natural infrared it gives off to the environment. We literally glow in the infrared spectrum, even if our naked eyes cannot perceive it.

17. Passive Infrared Sensors Can Detect Motion

Passive Infrared Sensor., , via Wikimedia Commons

A common technology that relies on human infrared emissions is the humble motion detector. Passive infrared (PIR) sensors can pick up the movement of people and animals based on detecting their infrared radiation.

Inside a PIR detector are chambers with infrared-sensitive elements, each tuned to a different part of the infrared spectrum. When a warm body like a human enters the field of view, it emits infrared that is absorbed by the sensor

18. Near Infrared is Used in Fiber Optic Communications

Fibre-optic cable and two fibre splicers in a Telstra pit/duct. , , via Wikimedia Commons

Near infrared wavelengths from 0.75 to 3 microns are commonly used in fiber optic communications. Optical fiber transmits data over long distances by sending pulses of light through an ultra-pure glass core. Infrared waves in the near-IR band can travel for dozens of kilometers through fiber with minimal signal loss.

By modulating the intensity of near-IR laser light, fiber optic networks can encode data signals for broadband internet, telecom services, computer networks and high-speed communications. Near infrared benefits fiber optics thanks to its ability to transmit through glass with less scattering, dispersion and absorption compared to visible light. Plus, near-IR sources like LEDs and lasers are highly efficient and stable.

Fiber optic telecom relies on specific near-IR windows with minimal transmission losses in silica glass fibers. The original window at 850 nanometers enabled early fiber networks. The 1300 nm window came next, followed by bandwidth at 1550 nm where fiber optics operate today. As new near-IR bands are utilized, data rates continue to multiply to keep pace with our information age built on invisible beams of infrared light.

19.  Some Materials Glow via Infrared When Heated

You may have seen signs or displays that seem to glow in the dark without any apparent light source. Many of these effects come from materials that emit visible light when exposed to infrared. By selectively giving off visible photons when struck by infrared waves, these materials create a visible glow.

For example, the black writing on some street and highway signs contains rare earth phosphors. As infrared radiation from car headlights interacts with the phosphor, it gives off a fluorescent green glow that reflects back to the driver. Glow in the dark toys also contain phosphors designed to absorb any ambient infrared, such as from body heat, and re-emit that energy as visible light.

Even some minerals and compounds in nature demonstrate this infrared-to-visible conversion in a phenomenon called tenebrescence. Varieties of hackmanite will glow a vibrant orange when heated by strong incandescent or fire light. So, while infrared itself remains invisible to us, specialized materials can harness its energy for dynamic visible displays and effects.

20. The Sun Emits Infrared As Well As Visible Light

Sun, image. , , via Wikimedia Commons

We think of the sun emitting warm yellow sunlight. But the sun actually gives off a broad spectrum of electromagnetic waves far beyond just visible light. Much of the sun’s energy reaches Earth in the form of invisible infrared radiation.

While the sun peaks in the visible range, it also produces strong ultraviolet rays, infrared waves, radio emission and even X-rays. Across all wavelengths, sunlight provides Earth with 175 petawatts of radiation. Around 53% is infrared while only 43% is visible light. The remaining 4% is ultraviolet.

Solar irradiance peaks at a 500-nanometer wavelength in the visible domain. But a second peak occurs at 1 micron in the near-infrared. Water vapor in Earth’s atmosphere absorbs infrared in bands centered around 1 micron. This absorption and reemission of infrared solar energy helps drive circulation in the atmosphere that transfers heat from the equator toward the poles.

Different layers of the sun emit at different wavelengths. But overall, the majority of the sun’s energy output actually resides in the infrared portion of the spectrum. Photosynthesis relies on visible light, but infrared emissions also deliver crucial warmth and drive weather patterns through atmospheric interaction.

21 – Infrared Lasers Are Used in Surgery

A 7W solid-state laser with an amplifier., , via Wikimedia Commons

Lasers that generate intense beams of infrared radiation have revolutionized surgical techniques over the past few decades. Infrared medical lasers provide non-contact precision cutting that cauterizes as it goes, sealing blood vessels immediately.

The carbon dioxide laser produces infrared light around 10 microns, which is strongly absorbed by water-rich human tissue. This allows clean incisions with minimal collateral damage. Lower powered continuous wave CO2 lasers vaporize tissue pixel-by-pixel for resurfacing skin damaged by scars or wrinkles. In other cases, pulsed infrared lasers can destroy tumor tissue with violent, superheated plasma without harming adjacent areas.

Infrared surgical lasers find use in procedures for eyes and eyelids, the mouth and throat, brain tumors, cancers, kidney and gallstones, and more. Plastic surgeons employ infrared lasers for cosmetic skin treatments with excellent results and minimal recovery time. Compared to scalpels, infrared laser surgery often reduces pain, bleeding and infection risk. The precise cutting and tissue-interaction makes infrared ideal for diverse minimally invasive medical procedures.

22. Night Vision Goggles Amplify Existing Infrared

When you think of night vision devices, infrared usually comes to mind. But common night vision actually relies on amplifying tiny amounts of visible green light rather than infrared itself. The standard night vision goggles used by the military operate based on image intensification.

A photocathode converts the sparse photons of ambient visible light into electrons. These get accelerated through a microchannel plate that slams them into a phosphor screen, emitting it back out as a green image bright enough for our eyes to see. The photons are from a 535nm green spectral line naturally emitted by trace chemicals in the air. An infrared illuminator can augment natural light when needed.

True thermal imaging does directly detect infrared radiation. But the iconic lime green night vision relies on enormously amplifying miniscule pre-existing visible light under dark conditions. The output is still green despite originating mostly from infrared. Next generation devices seek to combine infrared and image intensification for true 24-hour vision in any lighting conditions for the warfighter.

23.  Common Plastics Block Infrared Transmission

transparent plastics.Photo by on

Many common transparent plastics that freely transmit visible light are actually quite effective at blocking significant portions of infrared radiation. Materials like acrylic, polycarbonate, and polystyrene absorb infrared thanks to their molecular bonds that resonate at IR wavelengths.

For example, 2mm of acrylic transmits over 90% of visible light from 400 to 700 nm. Yet past 700 nm in the near-infrared, transmittance rapidly declines to just 10-20% at 2 microns and 1% beyond 3 microns. At the mid- to far- infrared bands, acrylic is largely opaque. This principle applies to other plastics as well.

While a disadvantage for infrared optics or sensors, this selective IR opacity makes plastics useful for cheap infrared filters, shielding sensitive detectors from unwanted infrared noise sources. The military uses thin plastic sheets as “blackout curtains” to block night vision goggles from detecting interior infrared emissions. Plastics certainly have their benefits in the visible domain. But molecularly, many remain quite “infrared blind” despite being transparent.

24.  Some Animals Can See Infrared

rattlesnakes. , , via Wikimedia Commons

Humans and most mammals are confined to seeing the narrow band of visible light between around 400-700 nanometers. But some animals see beyond this visible spectrum into the infrared wavelengths.

For example, pit vipers like rattlesnakes can sense infrared radiation to target prey. Pits on the snake’s face act as infrared detectors that locate concentrated warmer areas on warm-blooded critters indicating the best strike location. Viper infrared vision is quite blurry but allows targeting warm bodies in total darkness. Other infrared-sensing snakes include boas, pythons and some water snakes.

Some insects like jewel beetles also detect far-infrared out to wavelengths of 4,000 to 8,000 nanometers. Their infrared organs sense forest fires at distances up to 50 miles! Rather than seeing crisp images, the beetles simply detect the intense heat of far-off blazes. So while no animal can see the full infrared spectrum, some creatures extend their vision into the infrared domain beyond the visible rainbow we humans experience.

25.  Infrared Radiation Exerts Radiation Pressure

Infrared photons may seem intangible since we cannot see their light, but they do impart physical force like any electromagnetic radiation. Specifically, infrared rays exert radiation pressure on any surface they strike thanks to their momentum. This occurs because infrared photons transfer momentum upon absorption or reflection to impart a small force.

In the vacuum of space, this radiation pressure from infrared photons becomes significant due to the lack of air resistance. Satellites and spacecraft orient solar panels and heat shields to harness or deflect this radiation pressure from infrared sunlight and the solar wind. Over years, the tiny but persistent force can gradually alter orbits when unaccounted for.

On Earth, the air scatters the momentum of infrared photons to prevent a noticeable radiation pressure. But highly intense and focused energy sources like industrial lasers still witness measurable photon pressure effects. For example, a 1 kW 10-micron infrared laser can impart around 3 millinewtons of force, enough to levitate small particles. So, while invisible and intangible, concentrated infrared radiation does subtly interact with matter through observable radiation pressure effects.

26.  Infrared Photography Reveals Hidden Details

Infrared Photography. , , via Wikimedia Commons

Infrared photography captures wavelengths of light beyond what the human eye can see, revealing a surreal look at the world. Plants and foliage often appear white because they strongly reflect infrared. Skies can turn black as atmospheric water absorbs IR. And skin imperfections become more pronounced under infrared.

Infrared is sometimes split into near, mid and far categories based on the wavelength. Near-IR from 700-1400nm offers the most detailed imagery with specially modified digital cameras. Mid-IR from 1,400 – 3,000nm produces dreamlike black-and-white images full of contrast. Far-IR from 3,000 – 14,000nm sees thermal signatures of heat.

Law enforcement utilizes infrared to surveil suspects at night. Scientists study plant health through infrared aerial photography. Fine art photographers use infrared for stunning, otherworldly landscapes and portraits. Even smartphone camera apps now simulate infrared filters. Just be sure to avoid aiming infrared cameras at intense IR sources like the sun to prevent sensor damage. Overall, infrared photography opens up radical new artistic possibilities.

27.  Many Remote Controls Use Infrared

Infrared Light from the LEDs of a Windows Media Center remote control. , , via Wikimedia Commons

From TV and stereo remotes to even car keys, infrared light enables wireless control of technology all around us. Handheld remotes transmit coded instructions using infrared LEDs that are received by photosensors on devices. This allows commands like power, volume and channel control to be sent without any physical connection.

Infrared remote controls have some advantages over radio signals. Infrared does not pass through walls as readily, so devices only respond to the remote in the same room rather than accidental commands from adjacent rooms. Infrared transmitters and receivers also add minimal cost to products compared with radio frequency wireless. And narrow-beam infrared allows highly directional point-to-point communication.

However, infrared remotes have some limitations too. They require a clear line of sight to function properly since objects readily block the relatively short-range infrared beams. And they can face interference from intense ambient light sources. But overall, inexpensive infrared LEDs continue to provide an easy means of short-distance wireless control over common consumer gadgets.

28.  Meteorites Warm Up Upon Entering Earth’s Atmosphere

When meteors and meteorites plunge through the atmosphere, the extreme speeds lead to rapid heating from friction and pressure. Infrared radiation emitted from the heated exterior reveals details about a meteor’s size, composition and structure.

Special IR cameras are able to capture video of meteors flaring brightly as they speed through the upper atmosphere. As kinetic energy converts to heat, the meteorite glows infrared, allowing tracking of meteor trajectories and orbits. By measuring the infrared emissions, NASA scientists also study the object’s mineral makeup and physical properties during descent.

Occasionally, large meteorites make it all the way to the ground. But smaller fragments usually vaporize from extreme infrared heating miles above the surface. The intense infrared flaring as meteorites disintegrate provides clues to their origins and behavior. Rather than physical samples, infrared meteor observations give insights into material from distant parts of the solar system falling to Earth on a daily basis.

29.  Some Materials Transition from Transparent to Opaque in Infrared Domain

While glass is fully transparent to visible light, its behavior changes in the infrared portion of the spectrum. As wavelengths increase beyond visible red, glass starts to absorb more and more infrared radiation. This absorption leads to opacity in the mid- to far-infrared bands.

On the other hand, other materials like silicon that absorb visible light become largely transparent to certain infrared wavelengths, especially longer far-infrared. So, a material’s opacity or transparency can completely flip between visible and infrared domains.

This leads to selective use of materials like silicon, germanium and gallium arsenide for infrared optics. Meanwhile, visible optics rely on glass, polycarbonate and acrylic. An ideal visual telescope lens would ruin infrared performance and vice versa. The transition from transparent to opaque across the infrared boundary leads to specialized material selection optimized for either visible or infrared radiation.

30.  Microbolometers Convert Infrared Radiation into Electrical Signals

Microbolometers., , via Wikimedia Commons

A microbolometer is a specialized detector that converts incoming infrared radiation into a usable electrical signal. It consists of an array of miniature sensing elements with a material that changes resistance based on exposure to infrared wavelengths.

Each sensing pixel contains a vanadium oxide or amorphous silicon thermistor that heats up when struck by infrared photons. By measuring the changing resistance, the infrared signal gets translated into a voltage readout. The voltage feeds into external imaging circuits.

Microbolometer arrays are the basis of modern infrared thermal cameras for industrial, scientific and military use. They provide affordable imaging technology by directly transducing infrared energy into electric signals that feed standard video processing. While insensitive to visible light, microbolometers opened up infrared wavelengths to highly detailed real-time observation rather than slow film exposures.

From powering fiber optic internet to enabling night vision, infrared radiation profoundly shapes human technology and perception despite being imperceptible to us. We have explored some of the myriad ways that these unseen rays make modern life more productive and convenient while expanding scientific understanding of the world around us.