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Lecture Demonstrations Laboratory

Physics Rm. 202

(434) 924-6800


The Demonstrations Manual


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Harmonic Motion
Waves
Acoustics
Instruments
Sonometer
Open / Closed Resonance Tube
Resonant tunning fork
Dancing Flames (Ruben's Tube)
Air Driven Organ Pipe
Singing Tubes and Rods
Chladni Figures
Breaking of a Wine Glass

Chladni Figures

Purpose:

To demonstrate different vibrational resonances of thin plates.

Procedure:

Attach support rod to the plate and clamp to the edge of the table so that the plate is horizontal. Sprinkle sand over the surface and bow the edge of the plate with the bow in the vertical position. Many different modes can be obtained by bowing in different spots and by placing a finger along the edge of the plate. This does take considerable pratice to be effective.

Hints:

Using a PASCO or other wide range generator is much easier. Most cool looking shapes are at the high(er) (around 1KHz) frequencies. Start with small amount of "sand", listen to the increased amplitude of the annoying high frequency sound and sprinkle more magic dust to get a good figure. Some additional patterns for square plate are provided in the picture gallery. They are 707, 776, 970, and 1658 Hz oscillator frequency correspondingly.

Equipment:

  • Violin Bow
  • Chladni Plates
  • Table Clamp
  • Sand or Cream of Wheat
  • Mechanical Vibrator
  • Wave Generator