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3B SCIENTIFIC® PHYSICS
Kundt's tube U8432845
Instruction sheet
05/11 ALF
1 Movable plunger
2 Kundt's tube
3 Cork powder
4 Stand (not included)
5 Refill rail
1. Safety instructions
• Store the glass tube in a safe place where it
cannot be exposed to danger of shocks or
breaking.
• Do not expose the glass tube to any mechani-
cal stress or strain.
• Do not bend the movable piston while pushing
it in or pulling it out.
• Do not use the apparatus, if the glass tube is
damaged.
• Protect the apparatus from humidity and dust.
2. Description
By employing cork dust, a Kundt’s tube is used to
demonstrate the distribution of nodes and antinodes in a standing sound wave. Using the apparatus, it is also possible to demonstrate that standing
waves are formed when a resonance condition is
fulfilled for sound wavelength λ and length s of the
vibrating air column in the tube such that:
s = n λ/2 for reflected waves with antinodes at the
open end,
s = (2n+1)λ/4 for reflected waves with nodes
(n = 1, 2….n) at the closed end.
The wavelength can be determined from the number of nodes n and the distance a between the first
and last nodes
λ = 2a/(n − 1).
The rod with the cork plunger seals the tube and is
used for changing the effective tube length to tune
the frequency of the resonant sound waves.
A whistle, a tuning fork or a loudspeaker driven by
a function generator can be used as a sound
source.
A funnel reduces the wave impedance at the opening of the tube. As a result, more sound energy can
be introduced into the tube.
2.1 Scope of delivery
1 Glass tube
1 Movable piston
1 Funnel
1 Whistle
1 Refill rail
3. Technical data
Tube: 600 mm
Internal diameter: 17 mm
Glass thickness: 1.5 mm
Movable plunger: 280 mm x 3 mm dia.
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4. Operation
In order to conduct the experiments, the following
apparatus is additionally required:
1 Tuning fork 1700 Hz U8431020 or
1 Pneumatic loudspeaker U8432680 with
1 Function generator U8533510
Cork powder U8432850
1 Metre scale U8401550
1 Stand for coils U8496150
• Use a refill rail to introduce a small quantity of
cork dust into the tube.
• Slightly tilt the tube and shake it gently till the
cork dust has uniformly spread throughout the
length of the tube.
• Position the Kundt’s tube on the stand so that
the strip of cork dust is at the bottom.
• Slowly rotate the tube along its length in order
to spread the cork dust along the walls too.
• For determining the wavelength with the whis-
tle, fit the tube with the funnel.
• For determining resonance conditions, conduct
the experiment without a funnel.
It is recommended that a 1700-Hz tuning fork be
used. The fork produces a resonant wavelength λ
of 0.2 m for the 0.6-m tube. When the wave is reflected at the open end, antinodes are produced at
both ends. When the wave is reflected at the closed
end, nodes are produced at both ends.
• Position the sound source right at the end of
the tube.
• If blowing a whistle, make sure that it is per-
pendicular to the tube. This is necessary to
prevent any air from entering the tube.
• When using a tuning fork, strike it and quickly
hold it with its prongs in the direction of vibration in front of the opening of the tube or the
funnel.
• When using a loudspeaker, gradually change
the frequency on the function generator to
identify the resonance frequency. Effective
range: between 600 Hz and 8000 Hz.
• To tune a closed tube to the resonant length,
gradually move the movable plunger.
Fig. 1 Determination of the wavelength
Elwe Didactic GmbH • Steinfelsstr. 6 • 08248 Klingenthal • Germany • www.elwedidactic.com
3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany • www.3bscientific.com
Subject to technical amendments
© Copyright 2011 3B Scientific GmbH
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