The top two panes display waves that are traveling simultaneously in the same medium (same string, spring, air column, etc). Note that the two waves are traveling at the same speed in opposite directions and that they have the same amplitude and wavelength. The wave in the bottom pane is the superposition (algebraic sum) of the two component waves in the upper windows. The user is asked to answer some questions about these waves.
Is there a cost for using this resource?
No
Are there copyright restrictions?
Yes
Physlets, that is, the applets themselves, may be used to author new problems and these problems may be distributed along with the Physlet jar files for non-profit, educational purposes without requesting permission under certain conditions.
