What is infrared? THE infrared radiation (IR), or infrared light, is a type of radiant energy. It is invisible to human eyes, but we can feel it as heat. All objects in the universe emit some level of IR radiation, but two of the most obvious sources are the sun and fire.
IR is a type of electromagnetic radiation, a continuum of frequencies produced when atoms absorb and release energy. British astronomer William Herschel discovered infrared light in 1800, according to NASA.
In an experiment to measure the temperature difference between colors in the visible spectrum, he placed thermometers in the light path within each color in the visible spectrum. He observed an increase in temperature from blue to red, and he found an even warmer temperature measurement just beyond the red end of the visible spectrum.
electromagnetic spectrum
Within the electromagnetic spectrum, infrared waves occur at frequencies above microwaves and just below those of visible red light, hence the name “infrared”. Infrared radiation waves are longer than those of visible light, according to the California Institute of Technology (Caltech).
IR frequencies range from about 3 gigahertz (GHz) to about 400 terahertz (THz). Wavelengths are estimated between 1,000 micrometers (µm) and 760 nanometers (2.9921 inches). However, these values are not definitive, according to NASA.
Similar to the visible light spectrum, which ranges from violet (the shortest wavelength of visible light) to red (longer wavelength), infrared radiation has its own range of wavelengths. wave.
The shorter "near infrared" waves, which are closer to visible light in the spectrum electromagnetic, emit no detectable heat and are discharged from a TV remote control to change the channels.
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The longer "far infrared" waves, which are closest to the microwave section of the spectrum electromagnetic radiation, can be felt as intense heat, such as the heat of sunlight or fire, according to NASA.
IR radiation is one of three ways heat is transferred. The other two are convection and conduction. Everything with a temperature above 5 degrees Kelvin (minus 268 degrees Celsius) emits IR radiation.
The sun emits half its total energy as IR. Much of the star's visible light is absorbed and re-emitted as IR, according to the University of Tennessee.
household uses
Home appliances such as lamps Toasters and toasters use IR radiation to transmit heat. Industrial heaters like those used to dry and cure materials also utilize IR. At incandescent lamps they convert only about 10% of their electrical energy into visible energy, while the other 90% is converted into infrared radiation.
Infrared lasers can be used for point-to-point communications over distances of a few hundred meters. TV remote controls that rely on infrared radiation emit pulses of infrared energy from a light-emitting diode (LED) to an infrared receiver on the TV. The receiver converts light pulses into electrical signals that instruct a microprocessor to execute the programmed command.
infrared detection
One of the most useful applications of the infrared spectrum is in detection. All objects on Earth emit IR radiation in the form of heat. This can be detected by electronic sensors, like those used in night vision goggles and infrared cameras.
A simple example of such a sensor is the bolometer. It consists of a telescope with a temperature-sensitive resistor at its focal point. If a hot body enters this instrument's field of view, the heat causes a detectable change.
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