3B22.10 – Standing Waves on a String

Demo video: https://youtu.be/E20lCVxFwtE

Description: This demo shows the phenomena of standing waves on a string, and how the numbers of nodes changes with frequency.

Equipment:

• Wave driver
• Wave driver power supply
• String
• Ring stand
• Black background

Setup Procedure:

1. place the wave driver and ring stand on the bench and connect the wave driver to its power supply
2. tie one end of the string to the tip of the wave driver and the other end to the ring stand
3. place the ring stand far enough away from the wave driver so that the sting is taught and level with the tip of the wave driver
4. set up the black background behind the string so it is clearly visible
5. turn on the wave driver to test that it will vibrate the string correctly, adjusting the ring stand as necessary

Demonstration Procedure:

1. starting at a low frequency, increase the frequency on the wave driver power supply until the first standing wave appears
2. increase the frequency again until the second standing wave appears (note the additional node and multiple of the fundamental frequency)
3. touch one of the nodes and note how the standing wave is undisturbed
4. continue displaying further standing wave patterns
5. turn off the wave driver power supply when finished

Concepts: This demonstration shows how multiples of the fundamental frequency create standing wave patters in the vibrating string. This concept of harmonics is a very versatile idea and is used to model multiple more advanced concepts in other areas of physics.