In a cyclotron, the frequency of the particle's revolution is given by:
\[
f = \frac{qB}{2\pi m}
\]
where \( q \) is the charge of the particle, \( B \) is the magnetic field, and \( m \) is the mass of the particle. Rearranging to solve for \( B \), we get:
\[
B = \frac{2\pi m f}{q}
\]
Substitute the given values:
\[
B = \frac{2\pi (3.3 \times 10^{-27}) (12 \times 10^6)}{1.9 \times 10^{-19}} \approx 1.6 \, {T}
\]
Hence, the correct answer is (b).