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Radioactivity:
Elements having atomic number greater than 82 such as plutonium (Z = 84), Radium (Z = 8), Uranium (Z = 92) etc. are unstable by nature. These elements continuously emit different types of powerful radiations. This phenomenon is known as radioactivity.
The atoms of these elements, as a result of emission of these radiations undergo a process of decay and they gradually transform into the atoms of some other elements (daughter element).
Radioactivity is an irreversible process which continuous all the time. As it is an inherent and natural characteristic of radioactive elements, radioactivity exhibited by these elements is known as natural radioactivity.
Experiment to distinguish three kinds of radioactive rays
Soon after the discovery of radioactivity, Rutherford and other scientist s found out that radiations emitted from radio-active elements are of three types, named as Alpha, Beta, and Gamma rays, which are known as nuclear radiations or radio-active radiations.
These radioactive rays come from the nucleus of an atom. The three types radioactive rays can be distinguished from one another by a simple experiment.
Background radiations
Background radiation is the general term given to all natural and artificial radiation that is present in the atmosphere.
Some of the sources are cosmic rays and radon gas released by earth’s crust.
An additional, small percentage comes from man-made items like luminous dials, nuclear weapons tests, burning fossil fuel, and nuclear medicine.