# Some ideas for home experiments: waves

Students generally enjoy devising their own investigations, using materials readily found at home. From time to time, this can be a good alternative to standard homework, especially when it leads to writing short reports or oral presentations. Home experiments give valuable practise with practical problem-solving and with conceptual thinking.

1 Standing waves in a rectangular tank

It is easy to excite water into a 'slopping' mode, which is why it is hard to carry pans of water. Ask students what they can say about the Q (quality factor) of this system. It may be possible to excite other modes of oscillation using the plunger, for example, by moving it up and down in the middle of a large tank of water, and in other positions.

2 Standing waves under a running tap

Holding a knife-blade about 2 cm below a smoothly running tap, look for standing waves in the water flow. How does the pattern depend on the speed of water flow? On the separation of knife and tap?

3 Step waves under a running tap
Water flowing down from a tap onto a flat surface, such as the under-surface of a baking tray, shows a strange discontinuity: as the water flows away from the impact point, there is a step-like increase in its depth, at a distance r all round the impact point. Find out what factors affect r and try to explain this phenomenon.

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