infrared

Etymology

infra- + red

noun

1. (uncountable) The electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation, having a wavelength between 700 nm and 1 mm.
   Collisions of these 'transparent' molecules with the molecules that do have absorption bands in the infrared can have a considerable influence on the intensities of the observed absorption bands. 1962, John Nelson Howard, Transmission of the Atmosphere in the Infrared: A Review, page 3
2. (countable) A specific wavelength in this range.
   Sonne has shown that by means of the luminous rays the temperature in the tissue may be raised to a higher degree than by the use of the infrareds. 1924, The American Review of Tuberculosis, page 110
   Exposure of spectral pieces at centimeters, millimeters, and infrareds, which provide a top steadiness of the dependence "MCW radiation vs. parameter Δt" and its interannual (seasonal) dynamics. 2009, Alexander Grankov, Microwave Radiation of the Ocean-Atmosphere: Boundary Heat and Dynamic Interaction
3. (countable) A device that emits infrared radiation.
   In his room, he could install his infrareds without being discovered. 2000, Pete Fowler, Keeps, page 62
   Beams are the active counterparts of passive infrareds (PIRs). Since these are active infrareds, they require two parts: a transmitter and a receiver. 2007, Ed Morawski, Solving the Security Puzzle, page 79
   Additionally, infrareds tend to cook food faster so there's less time to render said fat. 2020, Jenny Dorsey, The Infrared Grill Master: Recipes and Techniques for Perfectly Seared, Deliciously Smokey BBQ Every Time

adj

1. Having a wavelength in the infrared spectrum.
2. (figurative, physics) Relating to very low energies or very large distances or time spans.
   Unless otherwise stated, we will be working in Euclidean space compactified to a sphere in order to avoid infrared problems. 1986, Luis Álvarez-Gaumé, “An Introduction to Anomalies”, in G. Velo, A. S. Wightman, editors, Fundamental Problems of Gauge Field Theory, page 97
   Secondly, as stated already by Osborne & Provenzale, pure k-behaviour is impossible since there would have to be infinite power at zero frequency (this would correspond to an infrared catastrophe). 2000, Andreas Galka, Topics in Nonlinear Time Series Analysis: With Implications for EEG Analysis, page 176
   Although infrared divergences are of long-distance nature, they often play an essential role in the verification of the validity of the perturbative treatment of short-distance phenomena. 2010, Taizo Muta, Foundations of Quantum Chromodynamics: An Introduction to Perturbative Methods in Gauge Theories, 3rd edition, page 331