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How to Detect Radioactivity

Unstable atoms produce radiation by throwing off bits of themselves as the atoms undergo radioactive decay. Though these particles have high energies, you cannot see, smell or feel them. To detect radioactivity, you need an electronic device called a Geiger counter. It has a sensor called a Geiger-Muller tube which generates an electrical impulse when a radioactive particle passes through it. A circuit amplifies the impulses, counts them and turns them into audible clicks. An analog dial or a numeric read-out displays the radiation rate in units of rems or sieverts.

Things You'll Need

Geiger counter
Watch
Pencil and paper
Calculator

Instructions

- 1
  Set any potentially radioactive materials at least 10 feet away from your Geiger counter. You will measure them after a brief setup.
- 2
  Turn the Geiger counter on. Turn its sensitivity control to its most sensitive setting. You will hear a slow clicking if you have the sound turned on.
- 3
  Write down the counter's reading every 60 seconds for 10 minutes. It will increase and decrease randomly, as radioactivity is a random process. You are measuring what scientists call "background radiation" produced by minerals in the ground, stars and other objects. This is a nearly constant, low-level source of radiation that varies slightly between geographic locations.
- 4
  Total the readings on the calculator and divide by 10 to obtain an average reading. This is the average background radiation rate.
- 5
  Bring one radioactive source and set it approximately 6 inches in front of the Geiger counter's detector tube.
- 6
  Write down the counter's reading every 60 seconds for 10 minutes. Total the readings on the calculator and divide by 10 to compute the average. Compare this figure to the average background radiation rate. If the new figure is substantially higher, the object you just measured has radioactivity. If it is about equal to the background reading, the amount of radioactivity is either nil or too small to measure with this equipment.

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