Geiger-Müller tubes

Geiger-Müller tubes are used as a radioactivity detector. In the middle of the tube diameter, a wire is positioned. The glass wall has a metal coating that serves as the second electrode. The tube is filled with a low-pressure gas. If an ionising particle flies through the tube, the gas is ionised and a discharge occurs. The current flowing through the tube is sensed by an attached electronic circuit. If a speaker with an amplifier is connected, it is possible to hear the characteristic rattle which shifts to a strong noise if the radiation intensity becomes high.