Purpose:Demonstrate standing waves in a circular membrane.
Description:A circular wire loop (from M4) holds a soap film which is positioned in front of a loudspeaker (the rectangular box to the left of the soap film). It is illuminated by a bright point source which casts a reflected pattern on the screen as shown in the photograph. A sine-wave oscillator attached to the speaker can be tuned to obtain various standing wave patterns, which are defined by the bright lines in the reflected light. Some standing wave patterns are shown above.