Waves

• What is a ripple tank?

  A shallow glass tank with an oscillating paddle/needle that creates waves, illuminated from above so the waves can be seen on the surface below the tank.
• Basics step of the waves in liquid practical

  1. Set up the ripple tank with a lamp above it and white card/paper below it.
  2. Switch on the motor attached to the wooden rod, measure the wavelength of the waves being cast onto the card with a ruler.
  3. Count the number of waves passing a point in 10 seconds and calculate the frequency, and then the wave speed.
• What type of waves are the waves on the surface of the water?

  Transverse Waves
• How much water should you put in the water tank?

  5 mm deep, if there is too much the rod won’t produce clear waves and will be less clearly projected onto the card below.
• How should the wooden rod be set up in the ripple tank?

  The wooden rod should be placed into the tank so that it just touches the surface of the water.
• How should you measure the wavelengths of the waves on the card?

  1. Adjust the lamp position so that the waves are clearly projected onto the card.
  2. Using a metre rule, measure across as many waves as you can.
  3. Divide the distance by the number of waves measured across.
• Why should you measure across more than one wave?

  To reduce the uncertainty in the measurement and improve the accuracy of the value.
• How can measuring the waves be made easier?

  Taking a photograph with the ruler in the picture so the waves can be measured without them moving.
• How do you measure the frequency of the waves on the card?


  Count the number of waves passing a chosen point in 10 seconds, divide the number by 10 to produce a frequency in Hz.
• Describe another way of measuring wavespeed.

  Mark two points on the paper that are a fixed distance apart and use a stopwatch to time how long it takes for a wave to move between them, divide the distance by the time taken.
• Basic steps of the waves in a solid practical.

  1. Measure the length of all the rods being tested and suspend one of them from two clamp stands using rubber bands.
  2. Strike the rod and measure the peak frequency.
  3. Calculate the velocity of the waves in the rod, repeat for rods of different lengths and materials.
• What equipment is used to determine the frequency of a sound?

  A frequency detector, such as that of a music tuner or a phone app.
• How does the length of the rod relate to its wavelength?

  The wavelength of the wave at peak frequency will be equal to twice the rod’s length.