1 Introduction
Resonant waves can be generated when a disturbance such as an earthquake or tornado
moves down the edge of a bay or harbour. The qualitative e¤ect of such a disturbance
can be observed in a classroom, with minimal apparatus, on a small scale by anyone who
causes a partially
lled wineglass to sing(resonate) using a wet
nger. If one carefully
examines the surface of the liquid it is possible to see that four ridges or crests follow the
nger around the rim. The photographs below were obtained using a turntable (Apfels
idea [1]), milk as the liquid, a clear wineglass and a blackened wineglass. The surface of the liquid also exhibits other, smaller patterns called crispations (edge or cross waves
[6]) which we do not attempt to model here (see Figure 2): The vibration pattern of the
glass is called a quadrupole vibration in the literature and the e¤ect of this vibration
has undoubtedly been know ever since mankind discovered the delights of drinking liquids
from
ne glass containers. Indeed the e¤ect of a singing wineglass is noted in the literature
by the ever inquisitive Michael Faraday [2] in 1831!
We discuss a simulation of the crests (not the crispations) using mathematics easy
enough for senior undergraduates to understand as well as an animation of this e¤ect
using the CAS Mathematica.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:tut/oai:encore.tut.ac.za:d1001470 |
| Date | 01 July 2007 |
| Creators | Joubert, SV, Fay, TH, Voges, EL |
| Publisher | American Journal of Physics |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | |
| Rights | American Journal of Physics |
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