Theory:

Some of the units of radioactivity are:
  • Curie
  • Rutherford
  • Becquerel
  • Roentgen
Curie:
Curie is the quantity of a radioactive substance that undergoes \(3.7 \times 10^{10}\) disintegrations in one second.
The value is close to the activity of \(1\ g\) of radium \(226\). Curie is the oldest unit of radioactivity.
 
\(1\ curie\) \(=\) \(3.7 \times 10^{10}\) \(disintegrations\ per\ second\)
 
Rutherford:
Another unit of radioactivity is Rutherford.
Rutherford (\(Rd\)) is the quantity of a radioactive substance, which produces \(10^{6}\) disintegrations in one second.
\(1\ Rd\) \(=\) \(10^{6}\) \(disintegrations\ per\ second\)
 
Becquerel:
Becquerel (\(Bq\)) is defined as the quantity of one disintegration per second. The SI unit of radioactivity is becquerel.
Roentgen:
One roentgen (\(R\)) is the quantity of radioactive substance which produces a charge of \(2.58 \times 10^{-4}\) \(coulomb\) in \(1\ kg\) of air under standard conditions of pressure, temperature and humidity.
Roentgen measures the radiation exposure of \(\gamma\) rays and \(X\ -rays\).