The pupils build a string and change its length and tension. While doing so. they observe the phenomenon of changes in frequency.
In task 3 the harmonic components can be also made visible in the waterfall diagram or frequency analysis.
Task 4 is for advanced pupils. Here the equation for natural oscillation should be used first in order to calculate the propagation velocity on the basis of the basic frequency and then use the calculated values to determine the frequencies for the harmonic components.
The pupils
About 15 minutes are needed to build the string.
5 to 10 minutes each are required for the individual observations (tasks). Depending on how much fun the pupils are having, it can take somewhat longer.