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, ${\frac {-dN}{dt}}=\lambda N$ s^-1, s for second, dimensionally is it second minus one, i.e. inverse seconds.