Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds
 

Vibrations in a rubber sheet

Demonstration

Circular waves on a rubber sheet can produce a standing wave pattern.

Apparatus and materials

Signal generator

Loudspeaker, large

Xenon flasher

Rubber sheet

Retort stand bases and rods, 3

Boss and clamp

Aluminium ring, large

Rubber band (s)

Leads

Health & Safety and Technical notes


Read our standard health & safety guidance

Draw radial lines on the rubber to make the oscillations easier to see. 

Holding the sheet to the ring with a large rubber band makes it easy to make small adjustments to the evenness of the sheet’s tension. 
 
The larger the power delivered by the loudspeaker, the better. 

rubber sheet

Procedure


a Stretch the sheet over the large metal ring, as shown in the diagram. Make it as evenly stretched as possible. 

b Place the large loudspeaker below the ring and rubber sheet. 

c Drive the loudspeaker at frequencies in the range 10 to 100 Hz. Try a central position of the speaker first, and a low frequency. Raise the frequency gradually, looking and listening for the lowest mode, in which the centre of the rubber sheet rises and falls. The amplitude may be 10 to 20 mm at the centre. 


Teaching notes


At a higher frequency, with the speaker off centre, you can create a mode of oscillation in which the rubber surface tilts, one side rising as the other falls, the rim staying fixed of course. 

This is similar to the experiment Ring of standing waves
 
You may wish to link this demonstration to the wave-mechanical model of the atom, with electron waves fitting into the atom. 
 
This experiment was safety-checked in February 2006

 

Related experiments


Ring of standing waves