Final answer:
A thermometer is used to measure variations in temperature by using materials that expand or contract based on temperature. Different temperature scales, such as Fahrenheit, Celsius, and Kelvin, provide different reference points and units of measurement. Infrared radiation (pyrometers) can also be used to measure temperature by detecting the emission of infrared radiation from an object.
Step-by-step explanation:
The instrument used to measure variations in temperature is called a thermometer.
Thermometers work by using materials that expand or contract when heated or cooled. The length of a liquid column in the thermometer changes as the temperature changes. The most common types of thermometers are mercury or alcohol thermometers, which have a reservoir of liquid that expands or contracts based on temperature.
Temperature can be measured using different scales, such as Fahrenheit, Celsius, and Kelvin, which provide different reference points and units of measurement. Infrared radiation (pyrometers) are another type of thermometer that measure temperature by detecting the emission of infrared radiation from an object, such as the human body or a vent in an aircraft carrier.