Simple straight pulses
Practical Activity for 14-16
Observing what happens when straight wave pulses are produced in a ripple tank.
Apparatus and Materials
For each group of students
- Wooden rod
Health & Safety and Technical Notes
Beware of water on the laboratory floor. Make sure you have a sponge and bucket handy to mop up spills immediately.
Place the power supply for the lamp on a bench, not on the floor by the tank.
- Lay the rod in the tank and produce a pulse by giving it a tiny but sharp roll forwards and back (see diagram}. You may find that it is sufficient just to tap the rod. You can produce continuous waves by repeating this motion periodically.
- Ask: Do the ripples change as they move away from the rod? If so, how?
- Students should observe that the ripples are rather wide near the rod but become sharper as they move away.
- The ripples are sharpest when the filament of the lamp is parallel to them. (This is why special 48 W lamps are required.)
This experiment was safety-tested in February 2006