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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, it corresponds to one gram of radium-226. Recently defined as 1 curie = 3.7×1010radioactive decays per second. However, in this article, let us look at the SI unit of radioactivity and other units as well.

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.

## What is the SI Unit of Radioactivity?

The SI unit of radioactivity is becquerel (Bq) and this term is named after Henri Becquerel. Unit of radioactivity 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

There are usually three 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

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## Frequently Asked Questions – FAQs

Radioactivity refers to the amount of ionizing radiation released by a material.

### What is the SI unit of radioactivity?

The SI unit of radioactivity is becquerel (Bq).

### What was the older unit to measure the amount of radioactivity?

The unit for measuring the amount of radioactivity was the curie (Ci).

### What is the term used to measure the magnitude of radiation exposures?

The magnitude of radiation exposures is measured in the terms of radiation dose.

### Define 1 curie

1 curie = 3.7×10^10 radioactive decay per second.

Hope you have understood in detail about the SI unit of radioactivity as well as other radioactivity units like Curie, Becquerel, and Rutherford. Stay tuned with BYJU’S to learn about various interesting science and math concepts.