Activity (decay rate) (R = λN (activity = decay constant × surviving nuclei))

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R = λN (activity = decay constant × surviving nuclei)

What each symbol means

SymbolWhat it stands for
NUndecayed nuclei present
RActivity (decays per second, Bq)
λDecay constant (s⁻¹)

When to use this

Valid when daughter activity negligible or question isolates parent; units SI Bq = 1 decay/s.