Peer Review

Harmonics

Material Detail page

Bookmark

Overall Rating:

Content Quality:

Effectiveness:

Ease of Use:

Overview:: This simulation illustrates the transverse wave motion on a finite length string due to any combination of the fundamental frequency and the first three overtones. The user is able to adjust the amplitude of the different modes and let the simulation run continuously or step by step. The wave may be free at both ends, fixed at one end, or fixed at both ends. The composite motion (in black) and/or individual components (in different colors) can be displayed. A particle representation of the motion is also available.
Type of Material:: Java simulation in a browser window.
Recommended Uses:: Preclass or inclass demonstrations, reinforcement of material discussed in class by the Instructor, or homework assignment.
Technical Requirements:: This is a Java Applet.
Identify Major Learning Goals:: To help gain a qualitative understanding of the concept of harmonics, including the fundamental frequency and overtones and to understand the role of boundary condition on vibration modes.
Target Student Population:: High school and lower-division undergraduate.
Prerequisite Knowledge or Skills:: A background in the basic properties of a wave, types of waves, and interference of waves.

Rating:
Strengths:: The content presented in this simulation is good. The sum of the fundamental frequency and the various combination overtones is accurate. All possible cases are covered; the role of nodes and anti-nodes in boundary conditions is clearly shown.
Concerns:: The simulated frequency of the fundamental modes is the same for the three different boundary conditions, fixed ends, free ends, and one fixed end and one free end. If these are meant to be a simulations of the same strings, this is correct for the fixed ends and free ends cases, but is not correct for the fixed-free end case. In the latter case, the wavelength of the fundamental is twice that of the other two cases, and thus the frequency should be half. It should be pointed out to students that different boundary condition cases should be considered simulations of different strings.

The explanatory text is minimal and limited to the applet's operation.

Rating:
Strengths:: This applet is an excellent method for illustrating the concept of harmonics by allowing the user to change the amplitude of three overtones along with the fundamental frequency. There is enough room for changes so that a user can become familiar with a bevy of different situations. The inclusion of an option for both ends free is a nice extra. The particle motion option is also handy when observing the overall motion pattern (however, see below).
Concerns:: The particle motion option cannot be turned off when displaying components of the overall wave. This makes it difficult to follow the motion in the component waves. No explanation of the underlying physics is included (or linked to) by the applet site.

Rating:
Strengths:: There are no instructions; however the simulation is rather selfexplanatory for the most part. There are only four (4) variables and one (1) control that can be changed. The Java application downloads in just a few seconds. The lines are coloredcoded to distinguish between the fundamental frequency and the first, second, and third overtones. The amplitude percentages of the fundamental frequency and overtones are listed in a table below the simulation. These amplitudes can be adjusted easily with a slider bar.
Concerns:: The "Component" and "Particle" options interact in a way that is not completely clear. Checking the "Component" option turns on the particle display even though this option is not checked.

Also, as noted above, there is no explanation of the underlying physics associated with the applet; instructors using this applet will have to supply this for themselves.

Other Issues and Comments:: This is one applet in a collection of several dozen similar resources developed by the author. These all are focused simulations that consider a single physical situation.
Creative Commons: