Concepts

Standing waves

Overview

A string is driven by a function generator that is attached to an oscillator. By adjusting the frequency of the oscillation, the string can be used to demonstrate standing waves. A strobe light is used to see the motion of each mode.

Note: practice this demo in advance. Knowing the frequency of each mode is essential.

Details

Equipment

• [1] Function generator
• [1] Mechanical oscillator
• [1] BNC-banana cable
• [2] Lab stand
• [2] Steel brick
  
• [1] Aluminum rod
• [3] 90-degree clamp
• [1] Roll of string
• [1] Strobe light
• [2] Foam

Classroom Assembly

1. Place the lab stands about 70 cm apart. Clamp an aluminum bar to fix the distance between two lab stands. Put steel bricks on the lab stand bases to hold them down.
   
2. Mount an oscillator on one lab stand.
3. Attach one end of the string to the oscillator and the other end to a 90-degree clamp mounted on the other lab stand.
4. Connect the oscillator to a function generator.
5. Turn on the function generator and adjust the string tension until desired effect is obtained.
6. Place the strobe light below the string.
7. Use the foam to block direct light from the strobe.

Important Notes

• The use of strobe lights may induce seizure in people with epilepsy or photosensitivity, so warn students in advance

Script

1. Turn on the function generator and adjust its frequency.
2. Turn off the room light.
3. Turn on the strobe. Adjust the strobe frequency as required.
   
4. Change the function generator frequency as necessary.

Additional Resources