The sound of learning physics

Illustration by Guila Forsythe

As a wide card-board tube was placed over a steaming Chick-fil-A cup of water, a confused fifth period physics class looked at their instructor as if he was crazy. While the physics class was initially a bit puzzled, it turns out that one can learn the wonders of sound through a simple demonstration. Today, I learned that sound travels fastest through solids, but it also travels faster through a light gas versus a heavy gas. Oxygen and Nitrogen are relatively heavy gases when compared to something like water vapor. In the tube demonstration, the water vapor of the cup of hot water displaced the oxygen and nitrogen normally present in air. By changing the gas in the tube, the sound of a clap traveled faster through the water vapor air than the normal air. In order to prove this point, a microphone and computer data collecting device were used. It turns out that sound through water vapor crosses the length of the cup in a few tiny fractions of a second sooner than sound traveling through normal air. This simple but fascinating demonstration had the entire physics class on their toes. Not only did this example further our knowledge about sound, but it also showed the concept of speed of sound in a new, exciting way. These sorts of demonstrations keep the class interesting and fun while still managing to be challenging and still be, well, physics.

About the author: Lauren Formica- Junior at the Lovett School who enjoys anything environmental , is a proud debate nerd and has a passion for community service.