Progressive Wave
Light, Sound and Waves

Simple straight pulses

Practical Activity for 14-16 PRACTICAL PHYISCS

Demonstration

Observing what happens when straight wave pulses are produced in a ripple tank.

Apparatus and Materials

For each group of students

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.

Read our standard health & safety guidance


Procedure

  1. 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.
  2. Ask: Do the ripples change as they move away from the rod? If so, how?

Teaching Notes

  • 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

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