# Unit of Radioactivity

## Introduction:

Radioactivity basically refers to the particles which are emitted from nuclei as a result of nuclear instability. The unit for measuring the amount of radioactivity was the curie (Ci). initially, correspond to one gram of radium-226. Recently defined as 1 curie = 3.7×1010radioactive decays per second.

Radioactivity has the dimension length squared mass per time.

Thus when we talk about the unit of radioactivity the SI composite unit is kilogram meter squared per second. However, we will look at other units as well. There are usually three radioactivity units.

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## What is the SI Unit of Radioactivity?

The SI unit of radioactivity is becquerel (Bq) and this term has been kept after Henri Becquerel. It is defined as:

The activity of a quantity of radioactive material where one decay takes place per second

 1 becquerel = 1 radioactive decay per second = 2.703×10-11

### Other Radioactivity Units:

An older radioactivity unit is the curie (Ci) and the name has been taken from Pierre and Marie Curie.

• It is defined as that quantity of any radioactive substance which gives 3.7 X 1010s-1 disintegration (dps).
• Sometimes millicurie (mc) and microcurie (mc) are also used.

Another unit is Rutherford (rd) and it is defined as the amount of radioactive substance which gives 106 disintegrations s-1 (dps).

 1 curie = 3.7×1010 radioactive decays per second 1 becquerel = 1 radioactive decay per second = 2.703×10-11 Ci. 1 rutherford = 1.106 radionuclide decays per second