Which tool is commonly used to detect gamma rays?

A Geiger counter is specifically designed to detect ionizing radiation, including gamma rays. This instrument works by measuring the ionization produced by radiation in a gas-filled tube, generating an audible click or visual signal when gamma rays pass through. The Geiger counter is sensitive to beta particles and alpha particles as well, but its capability to detect gamma radiation makes it an essential tool in nuclear physics and radiation safety.

Photodiodes can detect light, including certain wavelengths, but they are typically not used for detecting gamma rays, which have much higher energy and require different detection techniques. A black light operates in the ultraviolet spectrum and is used for detecting fluorescence but is not sensitive to radiation like gamma rays. A thermometer measures temperature and has no application in detecting ionizing radiation.