Thermometers to measure body temperature or atmospheric temperature are familiar items. Their maximum temperature range is between about minus 5 degrees Celsius and 40 degrees Celsius-all you could feel is "a little too cold" or "a little too hot" if you touch an object in this range with your hand. How can you measure extreme temperatures ranging from minus 50 degrees Celsius to 500 degrees Celsius? Of course, you can't touch extremely cold or hot objects, and a regular thermometer would break.
In such cases, a radiation thermometer can be used. This amazing thermometer takes temperatures without touching an object, using infrared rays sent out by the substance. The temperatures of things vary: our body temperature is around 36.5 degrees Celsius; boiling water is about 100 degrees Celsius. Every substance radiates a certain amount of infrared, depending on its temperature. Therefore, you can tell an object's temperature by measuring the wavelengths of the infrared rays it emits.
Because of its characteristic, radiation thermometers are used in many ways, such as for objects that are hundreds of degrees and therefore are too hot to touch, or objects in motion. It is possible to measure the temperature of car tires or bullet train wheels even while they are spinning.

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