Resonance is one of the most beautiful physical phenomenon. It helps you to tune your radio to your favorite channel, cook your food in a microwave oven and a trained opera singer to break a glass. Resonance can cause some really dangerous situation too, like the Tacoma Narrow bridge collapse. Marching soldiers are told to break their stride while crossing a bridge to avoid its collapse due to resonance, the collapse will not be as dramatic as the Tacoma Narrow bridge.
Now, let me show you a beautiful experiment demonstrating the resonance of a surface. This experiment is called Chldini Plate experiment named after its discoverer, Ernst Chladni. He is known as the father of acoustics, which is the study of mechanical waves including sound, ultrasonic and infrasonic sound.
In this experiment, the patterns observed can be predicted with great precision using mathematical exercises. But I feel that the joy in observing the phenomenon should come before giving a mathematical explanation to it. Enjoy the video!
PS. I also found a cool book on sounds. Try it!