Image of a small dog taken in mid-infrared ("thermal") light (false color)

Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. The name means "below red" (from the Latin infra, "below"), red being the color of visible light of longest wavelength. Infrared radiation spans three orders of magnitude and has wavelengths between 700 nm and 1 mm. Image of a small dog taken in infrared light. ... Image of a small dog taken in infrared light. ... Electromagnetic radiation or EM radiation is a combination (cross product) of oscillating electric and magnetic fields perpendicular to each other, moving through space as a wave, effectively transporting energy and momentum. ... The wavelength is the distance between repeating units of a wave pattern. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. ... This page is about the radiation; for the appliance, see microwave oven. ... Red is a color at the lowest frequencies of light discernible by the human eye. ... Latin is the language that was originally spoken in the region around Rome called Latium. ... Color is an important part of the visual arts. ... To help compare different orders of magnitude this page lists lengths between 100 nm and 1 µm (10-7 and 10-6 m). ... A nanometre (American spelling: nanometer) is 1. ... A millimetre (American spelling: millimeter, symbol mm) is an SI unit of length that is equal to one thousandth of a metre. ...

Different regions in the infrared

IR is often subdivided into:

• near infrared NIR, IR-A DIN, 0.7–1.4 µm in wavelength, defined by the water absorption, and commonly used in fiber optic telecommunication because of low attenuation losses in the SiO₂ glass (silica) medium.
• short wavelength IR SWIR, IR-B DIN, 1.4–3 µm, water absorption increases significantly at 1450 nm
• mid wavelength IR MWIR, IR-C DIN, also intermediate-IR (IIR), 3–8 µm
• long wavelength IR LWIR, IR-C DIN, 8–15 µm)
• far infrared FIR, 15–1000 µm

However, these terms are not precise, and are used differently in various studies i.e. near (0.7–5 µm) / mid (5–30 µm) / long (30–1000 µm). Especially at the telecom-wavelengths the spectrum is further subdivided into individual bands, due to limitations of detectors, amplifiers and sources. Infrared radiation is often linked to heat, since objects at room temperature or above will emit radiation mostly concentrated in the mid-infrared band (see black body). Deutsches Institut für Normung (DIN, the German Institute for Standardization) is a German national organization for standardization. ... A micrometre (American spelling: micrometer), symbol µm, is an SI unit of length. ... Fiber Optic strands An optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Deutsches Institut für Normung (DIN, the German Institute for Standardization) is a German national organization for standardization. ... Deutsches Institut für Normung (DIN, the German Institute for Standardization) is a German national organization for standardization. ... Deutsches Institut für Normung (DIN, the German Institute for Standardization) is a German national organization for standardization. ... Heat (abbreviated Q, also called heat change) is the transfer of thermal energy between two bodies which are at different temperatures. ... Spontaneous emission is the process by which a molecule in an excited state drops to the ground state, resulting in the creation of a photon. ... As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ...

Plot of atmospheric transmittance in the infrared region.

The common nomenclature is justified by the different human response to this radiation (near infrared = the red you just cannot see, far IR = thermal radiation), other definitions follow different physical mechanisms (emission peaks, vs. bands, water absorption) and the newest follow technical reasons (The common silicon detectors are sensitive to about 1050 nm, while InGaAs sensitivity starts around 950 nm and ends between 1700 and 2200 nm, depending on the specific configuration). Unfortunately the international standards for these specifications are not currently available. Plot of atmospheric transmittance in the infrared region of the EM spectrum. ... Plot of atmospheric transmittance in the infrared region of the EM spectrum. ... General Name, Symbol, Number silicon, Si, 14 Series metalloid Group, Period, Block 14 (IVA), 3, p Density, Hardness 2330 kg/m3, 6. ...

Telecommunication bands in the infrared

Optical telecommunication in the near infrared is technically often separated to different frequency bands because of availability of light sources, transmitting /absorbing materials (fibers) and detectors.

• O-band 1260–1360 nm
• E-band 1360–1460 nm
• S-band 1460–1530 nm
• C-band 1530–1565 nm
• L-band 1565–1625 nm
• U-band 1625–1675 nm

The Earth as an infrared emitter

The Earth's surface absorbs visible radiation from the sun and re-emits much of the energy as infrared back to the atmosphere. Certain gases in the atmosphere, chiefly water vapor, absorb this infrared, and re-radiate it in all directions including back to Earth. Thus, the greenhouse effect, keeps the atmosphere and surface much warmer than if the infrared absorbers were absent from the atmosphere. Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... Absorption has a number of meanings: In physics absorption is a process in which particles of some sort encounter another material and are taken up by or even disappear in it. ... A Sun is the star at the center of a solar system. ... Atmosphere may refer to: a celestial body atmosphere, e. ... Water (from the Anglo-Saxon and Low German wæter) is a colourless, tasteless, and odourless substance that is essential to all known forms of life and is the most universal solvent. ... The greenhouse effect, first discovered by Jean Baptiste Joseph Fourier in 1824, is the process by which an atmosphere warms a planet. ...

Applications

Infrared is used in night-vision equipment, when there is insufficient visible light to see an object. The radiation is detected and turned into an image on a screen, hotter objects showing up brighter, enabling the police and military to chase targets. Night-vision is seeing in the dark. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ...

Smoke is more transparent to infrared than to visible light, so fire fighters use infrared imaging equipment when working in smoke-filled areas because it does not interfere with other devices in adjoining rooms - this is especially important in areas of high population density (IR does not penetrate walls). Firefighter with an axe A firefighter, sometimes still called a fireman though women have increasingly joined firefighting units, is a person who is trained and equipped to put out fires, rescue people and in some areas provide emergency medical services. ...

Infrared radiation can be used to remotely determine the temperature of objects (if the emissivity is known). This is termed thermography, or in the case of very hot objects in the NIR or visible it is termed pyrometry. Thermography (thermal imaging) is mainly used in military and industrial applications but the technology is reaching the public market in the form of infrared cameras on cars due to the massively reduced production costs. The emissivity of a material (usually written ) is the ratio of energy radiated to energy radiated by a black body at the same temperature. ... Thermography is a type of infrared imaging. ... Thermography is a type of infrared imaging. ...

IR data transmission is also employed in short-range communication among computer peripherals and personal digital assistants. These devices usually conform to standards published by IrDA, the Infrared Data Association. Remote controls and IrDA devices use infrared light-emitting diodes (LEDs) to emit infrared radiation which is focused by a plastic lens into a narrow beam. The beam is modulated, i.e. switched on and off, to encode the data. The receiver uses a silicon photodiode to convert the infrared radiation to an electric current. It responds only to the rapidly pulsing signal created by the transmitter, and filters out slowly changing infrared radiation from ambient light. Palm IIIxe PDA Personal digital assistants (PDAs or palmtops) are handheld devices that were originally designed as personal organizers, but became much more versatile over the years. ... The Infrared Data Association (IrDA) defines physical specifications communications protocol standards for the short range exchange of data over infrared light, for uses such as personal area networks (PANs). ... Various light-emitting diodes (5 mm reds, 3 mm greens and yellows) A light-emitting diode (LED) is a semiconductor device that emits incoherent monochromatic light when electrically biased in the forward direction. ... A lens is a device for either concentrating or diverging light, usually formed from a piece of shaped glass. ... For the musical use of modulation, see modulation (music). ... A datum is a statement accepted at face value (a given). Data is the plural of datum. ... General Name, Symbol, Number silicon, Si, 14 Series metalloid Group, Period, Block 14 (IVA), 3, p Density, Hardness 2330 kg/m3, 6. ... A photodiode is an electronic component and a type of photodetector. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ...

In infrared photography, infrared filters are used to capture only the infrared spectrum. Digital cameras often use infrared blockers. Cheaper digital cameras and some camera phones which do not have appropriate filters can "see" infrared, appearing as a bright white colour (try pointing a TV remote at your digital camera). This is especially pronounced when taking pictures of subjects near bright areas (such as near a lamp), where the resulting infrared interference can wash out the image. In Infrared photography, a filter that blocks most of the visible light spectrum and only lets infrared (IR) light pass through, is used. ... An infrared filter is a filter to remove visible light and only pass infrared light in different wavelenghts. ... A digital camera, as opposed to a film or video camera, uses an electronic sensor to transform images (or video) into electronic data. ... A blocker is the inverse of a filter, instead of blocking everything like the filter does, it lets everything else pass and blocks only the specified things. ... A digital camera, as opposed to a film or video camera, uses an electronic sensor to transform images (or video) into electronic data. ... A camera phone in use Camera phones are a type of cellphone which has a camera built in. ...

Infrared radiation spectroscopy is the study of the composition of (usually) organic compounds, finding out a compound's structure and composition based on the percent transmittance of IR radiation through a sample. Different frequencies are absorbed by different stretches and bends in the molecular bonds occurring inside the sample. Spectroscopy is the study of spectra, ie. ...

History

The discovery of infrared radiation is commonly ascribed to William Herschel, the astronomer in the early 19th century. Herschel used a prism to refract light from a hot source and detected the infrared, beyond the red part of the spectrum, through an increase in the temperature recorded on a thermometer. Sir Wilhelm Friedrich Herschel (November 15, 1738 Hanover - August 25, 1822 Windsor) was a German-born astronomer and composer who became famous for discovering the planet Uranus, and made many other astronomical discoveries. ... An astronomer or astrophysicist is a scientist whose area of research is astronomy or astrophysics. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... See: Prism (geometry) Prism (optics) Prism (band) PRISM is an abbreviation for Probabilistic Symbolic Model Checker PRISM was an aborted RISC processor effort at DEC, see DEC PRISM This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... This article refers to refraction in waves. ... A thermometer is a device used to measure temperatures or temperature changes. ...

Infrared