No. of mole \(=\frac{1 \times 10^{-6}}{60}=\frac{10^{-7}}{6}\)
No. of atoms \(=\) no. of moles \(\times N _{ A }\) \(=\frac{10^{-7}}{6} \times 6 \times 10^{23}=10^{16}\)
\(A=N_0 \lambda e^{-\lambda t}\)
For, \(t =0, A = A _0= N _0 \lambda\)
\(=1.5 \times 10^{-5} \times 10^{16}=15 \times 10^{10} Bq .\)