Demos: 1S-43 Standing Waves--Metal Plate I

A thin metal plate is supported horizontally by a vertical stand (rigidly attached). Fine sand is sprinkled on the plate and the edge of the plate is bowed using a string bass bow. The point of support is a node. Standing waves are set up on the plate and sand accumulates along points and lines of least vibration.

Have the video camera focused on the plate. Sprinkle sand uniformly over the plate and draw the bow along the edge to produce vibrations of the plate. Produce different patterns by grasping the plate edge at various locations with your thumb and index finger. Different patterns emerge, depending on the forced location of the node. Try the middle and corners to begin with. Experimentation will produce other modes.

Suggestions for Presentation: Remind the students of standing wave patterns produced along a single dimension. The suggest that if there are two degrees of freedom, standing wave patterns can be produced in a plane. You might want to show with this demo, the video of the drum head vibrating. See the video disc Cinema Classics, Disc 2, Chapter 45.

Applications: Vibrating systems such as drum heads.

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Last Updated: May 9, 2016 11:44 AM