Ripples in the cosmic ice cream carton
My first year classes have been trying out one of the new practicals "resonance in a bucket". I've been looking for a good waves practical that doesn't rely on knowledge about standing waves ever since that went out of the syllabus. In this experiment a wave is sent back and forth across a plastic box. This ties in nicely (or gets students confused horribly) with SHM, since this isn't SHM its a wave travelling back and forth with constant velocity. The students seem to see this practical as something to do with oscillations and saw the time for two crossings as the time period rather than the time taken for the wave to cross the box twice. When asked to calculate velocity they didn't immediately see that the distance travelled for 10 "cycles" was 10 x the width of the box. Interesting how students find it difficult to change their train of thought.
Some of the results were very good by the way.