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

The unit is named in honor of Henri Becquerel. view more...