Eli5: infrared thermometers.
In: Physics
Objects emit [black body radiation](https://en.wikipedia.org/wiki/Black-body_radiation), for normal room temperatures it’s mostly infrared. Some objects reflect light, some emit a little in different spectrums on top of it (not all red objects are red hot), but generally they all emit black body radiation.
With black body radiation, the spectrum will change in a temperature dependent way (see the graph on the wiki). An infrared thermometer picks a couple points on the spectrum (in the infrared area) and then tries to figure out the shape of the black body spectrum given those points, from the shape it will know the temperature.
I believe most of the cheap ones just pick two wavelengths, calculates a slope between the intensity of those two wavelengths, and then uses a simple formula to convert the slope into a temperature.
Latest Answers