Geiger Counter Operation Explained

Geiger counters measure ionizing radiation. Radioactive substances produce this radiation by generating electrons that produce an electric current. The Geiger counter meter measures the output.

Radioactive Matter

• Radioactive matter produces high-energy subatomic particles that can ionize gas, detaching electrons from the molecules of the gas inside the Geiger counter. The gas can consist of helium, neon or argon.

Structure of the Counter

• The Geiger counter consists of a metal tube containing ionizable gas. The tube also has a thin wire with a high positive charge.

Ionization

• The electrons from the radioactive substance enter the tube, collide with the gas molecules, and knock electrons off of them. As collisions continue, the number of free electrons increases.

Generation of Current

• Because electrons have a negative charge, the positively charged wire attracts them. The electrons accumulate around the wire and eventually generate a detectable electrical current.

Measurement of Current

• The Geiger counter meter reads the output current, whose intensity depends on the number of electrons in the tube. The counter either emits a series of clicks or has a visual display of current output.