Answer
230 Hz.
Work Step by Step
Find the linear velocity of the ripples: $v=\omega r$.
$$v=(33.333\frac{rev}{60s})(\frac{2 \pi rad}{rev})(0.102\;m)=0.3560\;m/s$$
This is the speed of the “waves” moving past the needle. Find the frequency of the waves.
$$f=\frac{v}{\lambda}=\frac{0.3560\;m/s }{0.00155\;m}\approx 230\;Hz$$