What Are Geiger Counters Used For?
Radiation--which is invisible to the human senses--was discovered in the late 19th century. Scientists and researchers needed to investigate this phenomenon, which led to the invention of devices that detect radiation such as the Geiger counter.
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Invention
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German scientist Hans Geiger was studying radiation in England in 1906, using gold foil and a screen to detect the alpha particles released by radioactive materials. Alpha particles are capable of permeating thin solid objects, so they would penetrate the foil and hit the screen. Geiger would count the flashes of light created by the impact of particle to screen, eventually leading the scientist in 1908 to invent a device that would more accurately count the alpha particles for him.
Uses
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The average Geiger counter measures radioactivity, but not radon gas, laser energy, radiation from neutrons or microwaves. However, radiation detection finds practical application in a variety of capacities. Geiger counters are used in areas where potential radiation leaks can occur such as a nuclear power plant or an X-ray lab as well as other emergency situations where firefighters, police and hazardous materials teams can assess the area for radiation. In other disciplines such as anthropology, archeology and mineral collecting, one can check found objects for radioactivity. Even in the home one can use a Geiger counter to ensure that everyday metal household objects aren't made with radioactive material.
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Function
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The primary instrument of a Geiger counter is the Geiger tube, a tube full of inert gas and surrounded by a thin material that the radiation can penetrate. The tube also contains a positive electrode (a wire running through the tube) and a negative electrode (the wall of the tube). Once the radiation enters the tube, it ionizes the gas, creating charged particles that go to the electrode to which the particle is oriented. The increased ionization creates an electric pulse, which is noted by the Geiger counter as a click. As the radiation increases, the rate of clicks accordingly increase.
Innovation
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While the initial Geiger counter only detected alpha particles, he developed a new version with Walther Müller in the 1920s that could detect other types of radiation. This model is known as the Geiger-Müeller counter. Further advances were made by others in the following decades, including a model that also detects neutrons.
Results
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The Geiger counter was not the sole scientific contribution of Hans Geiger. Rather, Geiger used his invention to make further discoveries. For example, in 1925 Geiger was able to observe the dissemination and energetic decrease of X-rays (called the Compton effect) as well as cosmic rays.
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