Infrared

Infrared is electromagnetic radiation with wavelengths longer than visible red light and generally shorter than microwaves. It spans near-, mid-, and far-infrared bands, with boundaries that vary by convention.

Electromagnetic spectrum: The full range of electromagnetic radiation, ordered by frequency or wavelength. Infrared occupies the region beyond visible red and before microwave radiation.
Thermal imaging: Imaging that maps temperature differences from the infrared radiation emitted by objects. It turns infrared emission into images of surface temperature patterns.
Visible spectrum: The portion of electromagnetic radiation detectable by the human eye, approximately 380 to 700 nanometers in wavelength. Infrared begins at wavelengths longer than the visible spectrum's red end.
Terahertz radiation: Electromagnetic radiation around the boundary between microwave and infrared bands, commonly spanning 0.1 to 10 terahertz. Its placement near the infrared–microwave boundary varies across classification conventions.
Black-body radiation: Electromagnetic radiation emitted by an idealized object whose spectrum depends on its temperature. Objects at everyday temperatures emit much of their radiation in the infrared.
Infrared astronomy: The study of celestial objects through their infrared radiation. Infrared observations reveal cool objects and regions obscured by cosmic dust.
Microwave: Electromagnetic radiation with wavelengths longer than infrared and shorter than radio waves. Microwaves lie beyond infrared at longer wavelengths and lower frequencies.
Radio wave: Electromagnetic radiation with wavelengths generally longer than those of microwaves. Radio waves occupy longer wavelengths than infrared, although band boundaries can overlap in usage.
Planck's law: A formula describing the spectral distribution of radiation emitted by a black body at a given temperature. It predicts how an object's temperature sets the wavelengths and intensity of its infrared emission.
Infrared communication: The transmission of information using modulated infrared radiation. Short-range devices use infrared light to send data without radio-frequency signals.

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