Radioactivity was discovered by H. Becquerel in 1896. Becquerel named with uranium radiation. Two years later, Marie Curie researching uranium radiation by using a tool made ​​by Pierre Curie, the Piezo electric gauges (Lamellar Crystals Usually Used For The Measurement of Weak Power Flow), and Marie Curie was able to prove that “the strength of uranium radiation is proportional to the number of levels uranium contained in a mixture of uranium compounds .

Radioactivity is a core capability that is notstable atoms to emit radiation and turns into a stable core. The process of change is called decay. Atomic nuclei are takstabil called radionuclides. Material that contains radionuclides called Radioactive Substances. The amount of radioactivity of a radioactive elements (radionuclides) are determined by the decay constant (l), which states the rate of decay per second, and part-time (t ½). Both these quantities are characteristic for each radionuclide.
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