why are there so many ways to measure radioactivity, like Röntgen, Becquerel and sievert

Question

why are there so many ways to measure radioactivity, like Röntgen, Becquerel and sievert

In: Physics

Answer 1

They measure [different things and in different measurement systems](https://www.remm.nlm.gov/radmeasurement.htm).

_Becquerels_ (and _Curies_) are radioactivity, _Gray_ and _rad_ are absorbed dose of radiation into a given mass of tissue,
_sievert_ and _rem_ are ‘equivalent dose’;
_coulomb/kg_ and _Röntgen_ are exposure.