Kundt’s Tube

Switch on the loudspeaker and using a potentiometer identify the sound frequencies at which a standing wave is formed. Watch the movement of the cork dust. Sound travels through the air in a longitudinal wave form – a sound wave which can be made visible using cork dust in the Kundt tube. From the sound source the wave proceeds to the other end of the tube where it is reflected and travels back. By combining the original and the reflected wave we receive the standing wave. A standing wave really does not move anywhere, but “stands in place”. The important points of the standing wave are the nodes and the antinodes of particle movement. In the standing wave the nodes and antinodes regularly alternate. On the potentiometer you can search out other frequencies at which a standing wave is formed again, but with different intervals between the nodes and the antinodes.