Ruben's Tube - Image by Derek Leadbetter at Duke Physics
On Sep 22 four student volunteers from the Physics Dept's Outreach Group joined the Chemistry Dept's Outreach Group for "An Evening of Science" in front of the French Science Building. Using demonstrations, the students explained two topics they learned in mechanics, Newton's 3rd Law and Waves. The image here is of a Ruben's Tube. The pipe has a speaker inserted in one end and the other end plugged. There is a line of small holes drilled along the top and a gas valve on the front - basically a long grill with a speaker in one end. (The Outreach group can cook hot dogs, too!) After turning on the gas and lighting, an amplified function generator sends a sine wave to the speaker at one of the tube's resonant frequencies. The flame heights will vary according to the sound pressure level at each hole thus the standing wave in flames.