Standing waves generated in the air inside a horizontal glass tube are made visible in the patterns formed in cork dust at the bottom of the tube. An aluminum rod with a disk attached is placed inside the tube and clamped at its midpoint. When the rod is rubbed correctly resonant vibrations in the rod couple to the volume of air inside the tube via the disk.

Instead of the aluminum rod, a speaker hooked up to a sine wave generator can be placed at the end of the tube The resonances can be found by tuning the frequency and seeing when nodes appear in the cork dust.

L2

PIRA DCS 3D30.50