Quickly and effectively demonstrate constructive and destructive interference! One tube rings at precisely 440 Hz, the other at 441 Hz. Strike the bars with the rubber mallet to make them both ring at the same time. When the two nearly identical waveforms combine, the resulting wave pattern's frequency is actually the difference between the two frequencies. Students will clearly hear the ensuing “beat frequency” as the tone pulsates “on” and “off” with a frequency of 1 Hz.
You can also show your students that nodes and antinodes exist in vibrating materials. Spread white powder, such as flour, over one of the bars and strike the bar with the mallet. As the bar vibrates, the white powder collects in the areas of least vibration-the nodes. At the antinodes, the white powder quickly scatters. Students will easily see that the pattern is similar to the appearance of nodes and antinodes in a vibrating string. Set includes both high-quality vibrating tubes, rubber mallet and instructions.