A radioactive source used in industrial thickness gauges contains a nuclide with a half-life of 12 days12\text{ days}12 days. The decay constant, λ\lambdaλ, for this nuclide lies between:
10−8 s−110^{-8}\text{ s}^{-1}10−8 s−1 and 10−7 s−110^{-7}\text{ s}^{-1}10−7 s−1
10−7 s−110^{-7}\text{ s}^{-1}10−7 s−1 and 10−6 s−110^{-6}\text{ s}^{-1}10−6 s−1
10−6 s−110^{-6}\text{ s}^{-1}10−6 s−1 and 10−5 s−110^{-5}\text{ s}^{-1}10−5 s−1
10−5 s−110^{-5}\text{ s}^{-1}10−5 s−1 and 10−4 s−110^{-4}\text{ s}^{-1}10−4 s−1
