Becquerel
The becquerel (symbol Bq) is the SI derived unit of radioactivity, defined as the activity of a quantity of radioactive material in which one nucleus decays per second. A petabecquerel is 1015 times a becquerel, [math]\displaystyle{ \frac{-dN}{dt}=\lambda N }[/math] s-1, s for second, dimensionally is it second minus one, i.e. inverse seconds.
The unit is named in honor of Henri Becquerel.
Becquerel Media
Graphic showing relationships between radioactivity and detected ionizing radiation
