Janet plays a tune using water filled glasses
Janet and I were at dinner and surrounded by a collection of different glasses which had been set for our upcoming meal.
We decided to carry out some pre-dinner science and filled the glasses with different amounts of water.
Janet wet her finger with a drop of water and ran it around the top of each glass, resulting in a beautful note being played. By changing the type of glass and the amount of water in each glass, she was able to show off her musical talents and play a tune!
This happens because the motion of Janets finger sticking and sliding across the top of the glass causes both the glass and the water to vibrate at a low frequency. This is called its resonant frequency and is the frequency that an object likes to vibrate at.
If you add more water the pitch of the note goes down because there is more mass to vibrate. This means that the resonant frequency is a bit lower and you end up with a lower pitch note. We can hear these vibrations as sound if they are at the right frequency for our ears and so by playing around with the amount of water in each glass you can create a tune of your own.