4.Main Content
Review for: Waves along a line of students
Author: Tim Hickson
I used this experiment to illustrate transverse and longitudinal waves and to help my students understand - and, I hope, remember - why transverse waves cannot move through a fluid but longitudinal ones can. This arose out of our studying Earthquake Waves and wondering why P-waves can pass through the liquid core but S-waves cannot.
We had earlier, looked at the difference between the two types of wave using springs, particularly a slinky, and a rope. The class was a group of easily distracted, Year 10 girls. They had been intrigued, and, forgetting to be 'cool', wanted to take part in the experiment where a transverse pulse is sent down a thick rope. I had challenged the 'receiver' not to let her hands be moved by the arriving pulse. That this proved an impossible task fascinated them as well as convincing them that energy was being transferred with the pulse - and also by waves.
Instead of using a spring with its linked coils, or a rope with its linked fibres, we then tried linked students. By then, having been surprised by what they had discovered with the rope, they wanted to see what would happen so they did not fool around. They observed that, once again, linked particles (students, this time) could convey both transverse and longitudinal pulses (we did not bother with waves as I wanted to move on and they seemed to take the corresponding wave behaviour as obvious). We then unlinked the students and showed how a transverse motion could not be propogated but - as long as the students were not too far apart - a longitudinal one could. We concluded with a useful discussion of the limitations of the model
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Updated 17 Mar 2004
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