Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

Simple circular pulses in ripple tanks


Good questions will encourage close observations of circular pulses in a ripple tank.

Apparatus and materials

Ripple tank and accessories


Water Dropper

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.



Single ripple in tankStart a single ripple somewhere in the middle of the tank and then making several such ripples one after the other. Show this can be done using: 

  • finger 
  • pencil to touch the water 
  • drop of water from an eye dropper 


  • What is the shape of the pulse as it travels out? 
  • Is the speed of travel the same in all directions? How can you tell? 
  • Is the speed the same near to the centre of the tank and at the edges? 
  • Is the water moving along with the wave pattern? Drop a scrap of paper onto the water to see if it travels. 

Let students suggest their own tests. Any materials that students suggest for a test can be fetched quickly; and if they suggest none, the problem had best be left unsettled. 

Teaching notes

1 Possible learning outcomes from this experiment: 

  • Students become more familiar with the ripple tank. 
  • They find that the water does not move out with the ripple. 
  • They learn what is meant by a circular ripple. 
  • They deduce that it is circular because – if the water is of constant depth – the disturbance travels with the same speed in all directions. 
  • They might deduce what happens to the ripple speed if the water depth increases. 

2 Pulses will be circular if the tank is level. A circular wave train demonstrates that waves travel the same distance in the same time. 

This experiment was safety-checked in February 2006

Related guidance

Using ripple tanks


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