PURPOSE: To demonstrate dramatically standing waves in a tube.
DESCRIPTION: A loudspeaker in one end of a four-inch diameter galvanized iron tube creates standing waves in propane gas in the tube. The gas emerges out of a series of small holes in the top of the tube, forming a long line of flames when lit. Any sound resonant with the length of the tube can create standing waves in the gas which are readily visible as a pattern in the height of the flames. Both rhythm and frequency response can be seen nicely in music. An oscillator or a voice introduced using a microphone and amplifier provided with the demonstration can be used as simple sources for the loudspeaker.
Click here for flame tube plans by Dick Heckathorn.
Click here for flame tube plans and photographs from Idaho State University.
REFERENCES: Available. (PIRA 3D30.50)
EQUIPMENT: Flame tube with audio oscillator, microphone and amplifier, and audiocassette player with audiocassette, permanently assembled on rolling stand as photographed.
SETUP TIME: 10 minutes.