Required practical

Determining the properties of a wave

A ripple tank can be used to measure and calculate frequency, wavelength and the speed of waves on the surface of the water. A ripple tank is a transparent shallow tray of water with a light shining down through it onto a white card below to more easily see the motion of the ripples created on the water's surface. Ripples can be made by hand but to generate regular ripples it is better to use a motor.

A ripple tank, on a table, with surrounding equipment including a lamp, power supply, motor and wooden rod.

Aim of the experiment

To measure the frequency, wavelength and speed of waves in a ripple tank.

Method

  1. Set up the ripple tank as shown in the diagram with roughly 1 cm depth of water.
  2. Adjust the height of the wooden rod so that it just touches the surface of the water.
  3. Switch on the lamp and motor and adjust until low frequency waves can be clearly observed.
  4. Measure the length of a number of waves then divide by the number of waves to record wavelength. It may be more practical to take a photograph of the card with the ruler and take measurements from the still picture.
  5. Count the number of waves passing a point in ten seconds then divide by ten to record frequency.
  6. Calculate the speed of the waves using: wave speed = frequency × wavelength.

Example results table

Length of 12 waves cmWavelength cmNumber of waves in 10 secondsFrequency HzWave speed cm/s
..............................

Risks & hazards

HazardConsequenceControl Measures
Electrical components near waterShock damage to componentsSecure electrical components before adding water taking care not to splash