This demonstration uses a Geiger-Muller counter and various radioactive sources to investigate the properties of radioactivity, including the types of radioactive emissions and the inverse square law. 

Curriculum Notes 

This demo can be used to acquaint students with the types and properties of radioactive emissions when radioactivity is being studied. Allow ten to fifteen minutes to perform this demo.

Lead Time 
One day of lead time is required for this project.
  • a Geiger-Muller counter
  • a beta source
  • a gamma source
  • "hot" FiestaWare (two stoneware plates with a radioactive uranium based orange glaze)
  • a Coleman lantern mantle
  • a two inch by two inch thick glass plate
  • a meter stick
  • a timer
  • a bagel (optional)

Place the radioactive sources on the table, turn the Geiger counter on to "audible"There are several possible variations of this demonstration depending on which principles of radioactivity you want to emphasize. The law of inverse squares can be demonstrated by varying the distance of the counter from the source and counting the signals over a given period of time. The relative penetrating power of beta particles and gamma rays can be compared by interposing the glass plate between the respective sources and the counter. The FiestaWare and lantern mantle can be used to demonstrate the use of radioactive materials in consumer items. One fun twist on the demonstration is to place a bagel on the FiestaWare at the beginning of the demonstration; at the end of the demonstration, use the counter to show that the plates are "hot" and offer the bagel to someone in class. 

Safety Precautions 

Though the level of radioactivity emitted by the sources is considered to be safe, it is always a good idea to minimize your exposure to radioactivity. The best way to do this is to minimize the time that you are near the sources. Exercise caution when handling the lantern mantle. The radioactive salts in it are friable and if you handle it you could get some of the dust on your hands and ingest some. Wash your hands thoroughly after handling it. 

Prep. Notes 

Obtain all of these supplies from the physics demo room.

© Copyright 2012 Email: Randy Sullivan, University of Oregon Chemistry Department and UO Libraries Interactive Media Group