Measuring the Wave Speed on a Wave Demonstrator

With information about travel time and distance, the wave speed on a 0.90 m short-rod wave demonstrator can be calculated.

Discussion

You can use a stopwatch to measure the elapsed time (start timing at the moment the pulse is generated and leaves one end of the demonstrator and stop timing after the pulse has traveled one or more lengths of the demonstrator) and distance traveled by a wave pulse (in multiples of the length of the demonstrator, 0.90 m) to find the wave speed. With this information you can calculate the wave speed in this short-rod demonstrator (about 1.38 m/s). Note that the wave speed in the short-rod demonstrator is greater than that in the long-rod demonstrator used in previous movies (about 0.24 m/s).

You can compare this value with those calculated from frequencies and wavelengths for standing waves in the next eight movies, using the relationship v = ƒλ. Since the end of the wave demonstrator coupled to the wave driver is not truly stationary, there are small discrepancies between the wave speed determined directly by measuring travel times and distances and those calculated using standing wave frequencies and wavelengths. You can fill in the following table and calculate wave speeds for each of these standing wave movies. You can compare your calculated wave speeds with the values shown on the answer page.