PURPOSE: To demonstrate interference of sound with two coherent sound sources in a quantitative way.
DESCRIPTION: The oscillator is set to approximately 3000 Hz, with identical signals being applied to both loudspeakers and displayed on the lower oscilloscope trace. The microphone, with its signal displayed on the oscilloscope upper trace, can be moved around to observe the interference pattern by displaying the alternating maxima and minima in the intensity pattern. Nodal and antinodal lines can be observed and measurements made to show the relationships between the wavelength, source separation, and the nodal/antinodal lines.
SUGGESTIONS:
REFERENCES: (PIRA 3B55.10) See also demonstration H2-22: INTERFERENCE TRANSPARENCIES, a Moire pattern model of this experiment, and H2-21: AUDIBLE YOUNG'S EXPERIMENT - GROUP LISTENING, for a more qualitative experiment using only group listening. See also several film loops using the ripple tank.
EQUIPMENT: Oscillator with loudspeakers on optical rail, microphone with mic amplifier, and oscilloscope.
SETUP TIME: 10 min.
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