thermal radiometry

Thermal radiation is the emission of electromagnetic radiation from a heated surface, traveling at the speed of light without needing a medium. This radiation spans from infrared to ultraviolet wavelengths, with its intensity determined by the surface's temperature, following the Stefan–Boltzmann law.1

A radiometer is an instrument used to measure this radiant energy, particularly infrared radiation. Radiometers can be thermal detectors, like thermocouples or bolometers, which measure temperature changes, or quantum detectors that sense individual energy quanta. The properties of a surface, such as its color, affect its ability to emit and absorb radiation; good emitters are also good absorbers, like a blackened surface.21