Experiments with Waves

• Measuring the speed of waves isn't that simple. It calls for crafty methods
• Use an Oscilloscope to Measure the Speed of Sound

  1. Attach a signal generator to a speaker to generate sounds with a specific frequency

  2. Use two microphones and an oscilloscope to find the wavelength of the sound waves generated

  3. Set up the oscilloscope so the detected waves at each microphone are shown as separate waves

  4. Move one microphone away until the two waves are aligned on the display, but have moved exactly one wavelength apart

  5. Measure the distance between the microphones to find one wavelength

  6. Use the formula to find the speed of the sound waves
• The speed of sound in air is around 130 m/s
• Measure the Speed of Water Ripples Using a Lamp

  1. Dim the lights and turn on the lamp - you'll see a wave pattern made by the shadows of the wave crests on the screen below the tank

  2. Measure the distance between shadow lines that are 10 wavelengths apart, then divide this distance by 10 to find the average wavelength

  3. Use the formula to calculate the speed of the waves
• This set-up is suitable for investigating waves, because it allows you to measure the wavelength without disturbing the waves
• Use the Wave Equation for Waves on Strings

  1. Set up the equipment with a signal generator, vibration transducer, string, pulley, and masses

  2. Turn on the signal generator and vibration transducer to start the string vibrating

  3. Adjust the frequency setting on the signal generator to change the length of the wave created on the string

  4. Measure the wavelength by measuring the length of all the half-wavelengths on the string in one go, then divide by the total number of half-wavelengths

  5. The frequency of the wave is whatever the signal generator is set to

  6. Use the formula v = f to find the speed of the wave
• This set up is suitable for investigating waves on string because it's easy to see and measure the wavelength (and frequency)