Standing Waves

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Using a speaker, a standing sound wave has been set up inside a tube. A movable microphone lies inside the tube. The display grid shows 10 centimeter intervals. The graph shows the display of an oscilloscope attached to the microphone. Move the microphone back and forth to study the changing amplitude of the sound it receives. Can you find the locations of nodes and antinodes due to constructive and destructive interference?


  1. For what microphone position(s) does the amplitude of the sound go to zero? What is such a location called?
  2. For what microphone position(s) is the amplitude of the sound a maximum? What is such a location called?
  3. From the locations of the nodes, can you determine the wavelength of the sound waves?
  4. From the graph, can you determine the frequency of the sound waves?
  5. Using the wavelength and the frequency, can you find the velocity of the sound waves in the tube?


See Serway and Beichner, Physics For Scientists and Engineers 5th Edition, Section 18.5

Illustration written by Steve Mellema