Geiger-Muller tube. Experiment with a radioactive source (lower left), a Geiger-Muller tube (lower right) and a ratemeter (centre). A Geiger-Muller tube is used to detect levels of of radiation. Radiation passing through gas in the tube ionises it, briefly allowing a current to flow. This electrical pulse is recorded, with radioactive intensity proportional to the number of pulses in a given time period. It can detect alpha, beta and gamma radiation. Speakers (upper right) are being used to amplify the click which is produced each time the gas is ionised.