Kundt's tube: Powder in tube shows standing waves.

Kundt's Tube: resonant frequency of a stroked rod causes nodal patterns in dust in a tube. The apparatus is clamped to a table. Plunger A is adjusted. The rod of Plunger B is stroked with a cloth impregnated with resin, causing the rod to resonate loudly (at first harmonic = 2,470 Hz). This excites powder in the glass tube to form patterns in the nodal regions. The frequency f of the resonating rod B can be determined,knowing the distance between the nodes. [f = (speed of sound divided by ) = (344m/sec)/.14m = 2457 Hz.]. Plunger B: Rod is clamped at midpoint. Plunger A: Rod is slid into tube, with black mark positioned under metal holder.