# Eli5: infrared thermometers.

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Eli5: infrared thermometers.

In: Physics

Basically how much heat from the infrared beam is absorbed / reflected from the heat source you are measuring can be calculated. The difference is equal to a specific temperature based on some mathematics. The result is your temperature.

Objects emit thermal radiation at a wavelength related to their temperature. You can’t see this light until it becomes quite hot, over 1000˚F (500˚C). However, special sensors can detect it, and those sensors are the thing inside the infrared thermometer that detects the temperature of the object you’ve pointed the thermometer at.

Yall anwsered within seconds crazy. Good shit tho thanks

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.

I didn’t see a true ELI5, so here goes: you know how we can see colors? Heat gives off “colors” too. The infrared thermometer can see those colors to tell you how hot something is.