How Everything Works
How Everything Works How Everything Works

Question 189

How can temperatures be taken accurately and so quickly in the ear?
The fancy ear thermometers used in doctor's offices are almost certainly measuring the thermal radiation emerging from inside the ear. They probably use a thermopile detector that responds very quickly to the thermal radiation that reaches them. Since the thermal radiation emitted by a black object (or from within a deep cavity such as the ear) is characteristic of the object's temperature, a quick study of that thermal radiation is enough to determine the person's temperature.

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