A dramatic demonstration, called singing rods, involves a long, slender aluminum rod held in the hand near

Question:

A dramatic demonstration, called “singing rods”, involves a long, slender aluminum rod held in the hand near the rod’s midpoint. The rod is stroked with the other hand. With a little practice, the rod can be made to “sing.” Or emit a clear, loud, ringing sound. For a 90-cm-long rod,
(a) What is the fundamental frequency of the sound?
(b) What is its wavelength in the rod, and
(c) What is the traveling wavelength in air at 20oC?