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Detection of Radioactivity

Introduces methods of measuring radiation and units used to quantify radiation.

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What is that Clicking Noise?

What is that Clicking Noise?


Credit: Linda Bartlett
Source: https://commons.wikimedia.org/wiki/File:Laboratory_%282%29.jpg
License: CC BY-NC 3.0

Radioactivity cannot be seen, but it can be detected. Ionizing radiation interacts with a detector in such a way as to give a discernible signal. With a simple device such as a Geiger counter we would hear a clicking. This instrument was often used in old movies to search for radioactive contamination or to prospect for uranium. The instruments today are much more sophisticated, much more expensive, and much heavier.

News You Can Use

  • Radioactivity is all around us. When a laboratory measures the amount of radioactivity in a sample, it is important to compensate for background radiation (that naturally occurring radiation). In a carefully maintained and shielded laboratory setting, the background radiation will be minimal. However, in the great outdoors, there may be a significant amount of background that we detect.
  • We are all exposed to radiation in our lives. The major source of exposure for most people is through X-rays. This is not radioactive exposure, but can produce some of the same effects on the body. If a nuclear medicine procedure is involved, a radioisotope is administered and the body then gets additional exposure.
  • Credit: Clyde Robinson
    Source: http://www.flickr.com/photos/crobj/763708714/
    License: CC BY-NC 3.0

    An X-ray scanner at an airport. These machines use low level X-rays to inspect the contents of your luggage [Figure2]

  • Very sophisticated instruments are used for laboratory detection of radioactivity. These machines are much more expensive and complex than the average concerned citizen wants to bother with. Geiger counters are now available that are the size of a cell phone and will give an actual read-out of the amount of radioactivity present. Dosimetersare badges or rings that can be worn to get an idea of radiation exposure over a period of time. They often employ a film that fogs up when exposed to the radiation. Scanning the darkness of the film will give an indication of exposure.
  • Watch the video at the link below to learn how a Geiger counter works:


Show What You Know

Use the links below to learn more about measuring radioactivity. Then answer the following questions.

  1. Which food has the highest level of radioactive potassium?
  2. What is the average yearly exposure to ionizing radiation?
  3. What is the primary source of natural radiation exposure for a person?
  4. Where does radon come from?
  5. Where is the best place to put a radon test kit?

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Image Attributions

  1. [1]^ Credit: Linda Bartlett; Source: https://commons.wikimedia.org/wiki/File:Laboratory_%282%29.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: Clyde Robinson; Source: http://www.flickr.com/photos/crobj/763708714/; License: CC BY-NC 3.0

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