The frequency of the emitted radiation when an electron in a hydrogen atom transitions between energy levels is given by the Rydberg formula:
\[
\Delta E = 13.6 \left( \frac{1}{n_1^2} - \frac{1}{n_2^2} \right) \, \text{eV}
\]
The frequency \( f \) is related to the energy \( E \) by:
\[
E = h f
\]
Thus, for the transition from \( n = 3 \) to \( n = 1 \), the frequency is twice the frequency for the \( n = 2 \) to \( n = 1 \) transition.
Given the frequency for \( n = 2 \) to \( n = 1 \) is \( 2.7 \times 10^{15} \, \text{Hz} \), the frequency for \( n = 3 \) to \( n = 1 \) transition is \( 3.2 \times 10^{15} \, \text{Hz} \).
Thus, the correct answer is (a).