Geiger Counter and Radiation Shielding

A Geiger counter is used to detect radiation from various sources. By placing paper, aluminum, and lead between the source and detector, students can compare the penetrating power of alpha, beta, and gamma radiation.

1. Turn on the Geiger counter and ensure the speaker is audible so clicks can be heard for each detection event.
2. Place a radioactive source (e.g., uranium ore, radium dial, smoke detector sample) under the detector and observe the count rate.
3. Place a sheet of paper between the source and the detector; note any reduction in counts.
4. Replace the paper with aluminum foil or a thin aluminum plate; record the effect on the count rate.
5. Place a lead plate between the source and detector; observe the much larger reduction, especially for gamma rays.
6. Compare results across different radioactive sources to highlight the types of radiation emitted.

Demonstrating the penetrating power of alpha, beta and gamma radiation - Simon Lloyd:

Radioactivity demo - alpha, beta, gamma with Geiger counter - MissLowePhysics:

📄 Geiger Counter - Simon Fraser University: https://www.sfu.ca/physics/demos/demos-experiments/geiger-counter-burnaby.html

• Use multiple Geiger counters to compare different shielding materials simultaneously.
• Test different thicknesses of aluminum or lead to find how much shielding is required to reduce the count rate significantly.
• Discuss real-world applications such as protective clothing, nuclear reactor shielding, and medical radiology.

• Handle all radioactive sources carefully and for the minimum necessary time.
• Wash hands thoroughly after handling radioactive samples.
• Do not allow direct contact of sources with skin or eyes.
• Keep sources stored in shielded containers when not in use.
• Handle unsealed items such as lantern mantles with extreme care to avoid spreading radioactive dust.

• Why does paper block alpha radiation but not beta or gamma? (Alpha particles are relatively heavy and cannot penetrate even thin barriers.)
• Why does aluminum stop most beta radiation but not gamma? (Beta particles are lighter and faster, but gamma rays are high-energy photons that require denser materials to absorb.)
• Why is lead effective at reducing gamma radiation? (Lead’s high density and atomic number increase the probability of gamma absorption.)
• How does this experiment connect to radiation protection in medicine and industry? (It illustrates why different types of shielding are used depending on the radiation involved.)