Radioactive Activity Calculator — A = λN

Activity measures how 'hot' a sample is: the decay constant times the number of undecayed nuclei. One becquerel is one decay per second.

How to interpret the result

A 1 Ci source (3.7×10¹⁰ Bq) undergoes 37 billion decays per second — the historical 'curie' was based on one gram of radium-226.

Assumptions

• Decay constant in s⁻¹
• Instantaneous activity (it falls as nuclei decay)