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Radiation and Radioactivity : Measuring Radiation
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While radiation cannot be seen, it can be measured very precisely -- much more precisely than other potentially hazardous materials. One of the basic measuring instruments is the Geiger-Muller counter. The instrument consists of a detector set at the end of a probe (the black tubular instrument shown in the photo) with counting electronics.&;nbsp This instrument counts the number of radioactive particles entering a sensitive detection chamber, and translates that signal into a needle movement on an analog dial in this case.
There are dials to change scales for different radiation densities, a sample source of radiation to calibrate the instrument (in the holder), and batteries inside the box for portability. It emits a click for every particle, so in background radiation the instrument clicks every few seconds, while in a high radiation environment it clicks rapidly in proportion to the radiation level. In this way the user gets a visible and an audible measurement of radioactivity.
Some people receive exposure to radiation as part of their employment. In such an environment, worker radiation exposures are carefully monitored to ensure that everyone's exposures are kept as low as reasonably achievable. Individual film badges and personal dosimeters are useful for this purpose. In the film badges the amount of film darkening is a measure of the radiation received, so by analyzing the film, radiation exposure records for each individual worker can be kept. Personal dosimeters allow the workers to view their own radiation dose instantly by looking at a small scale magnified by the instrument (which looks like a pen with a clip to mount it in a pocket).
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