What is a common tool used for measuring radiation doses?

The Geiger counter is a common tool used for measuring radiation doses due to its ability to detect and measure ionizing radiation. It operates by using a Geiger-Müller tube, which becomes conductive when radiation passes through it, creating an electrical pulse that can be counted and displayed as a reading on the device. This method is effective for various types of radiation, including alpha particles, beta particles, and gamma rays, making it a versatile instrument in both occupational environments and emergency situations.

Other instruments listed, such as a thermometer, are used for measuring temperature rather than radiation. A spectrophotometer is typically employed in laboratories for analyzing the properties of light and solving concentration of substances in solutions but is not designed to measure radiation levels directly. Similarly, a pH meter is used to determine the acidity or alkalinity of a solution and does not relate to radiation measurement. Thus, the Geiger counter stands out as the appropriate tool for assessing radiation doses.