One of my favorite physics demonstrations to perform at local schools, conventions, and expos is the production of Chladni patterns, such as the one shown below.
I’ve blogged about these patterns before. They are formed by vibrating a metal plate at one of its special resonance frequencies, which causes the plate to form standing waves. These waves have some locations — antinodes — where they vibrate a lot, and other locations — nodes — where they don’t vibrate at all. By sprinkling sand over the plate, the sand will be pushed to the nodes allowing the otherwise invisible vibrations to be visualized.
This technique is remarkably old, first published by German physicist Ernst Chladni in 1787; the patterns created are therefore known as Chladni figures. Chladni used a violin bow to excite his plate, but today we can use a speaker and frequency generator to produce the effect more readily.
I’ve been doing Chladni pattern demos for nearly five years, and when I recently did them again at a local school, I decided to spice things up with colored sand, to produce multicolored patterns. This results in lovely things such as the pattern below!
This became a bit of an art project for me, and I spent a couple of hours over the past few days making pretty colored Chladni patterns! I thought I would share the results here. In addition, I learned a little bit more about the physics of these patterns that I will share along the way.
Skulls in the Stars 