A simple, yet unusual, child's toy, in effect a rotating corrugated resonator, generates a wide range of tones by spatial modulation of air flow, and illustrates some of the most basic features of the physics of resonance, waves, and fluids. I encountered the toy when living in Japan with my family and brought some specimens to my laboratory to examine and work out the mechanism of sound production. Although production of sound and electromagnetic waves is quite different in detail, the toy calls to mind an equally unusual light source.

Read the paper (PDF, 1.2 MB)