From the given graph, we find the initial activity \( R_0 \) at \( t = 0 \) and its natural logarithm:
\(\ \ \log_e R_0 = 7.5 \)
Thus,\(\ R_0 = e^{7.5} \approx 75,000\)
The wavenumber of the first line (\(n_2 = 3\)) in the Balmer series of hydrogen is \( \overline{\nu}_1 \, \text{cm}^{-1} \). What is the wavenumber (in cm\(^{-1}\)) of the second line (\(n_2 = 4\)) in the Balmer series of He\(^{+}\)?