P12 Properties of waves

• The amplitude of a wave is the maximum displacement of a point on a wave, away from its undisturbed position
• The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave
• The frequency of a wave is the number of waves passing a point each second
• the period is the time (in seconds) for one wave to pass a point
• Transverse waves are waves where the oscillations are perpendicular to the direction of energy transfer
• The wave speed is the speed at which the energy is transferred through the medium
• Longitudinal waves are waves where the oscillations are parallel to the direction of energy transfer
• • Divide that length by the number of waves to find the wavelength of the waves
  • Record the wavelength value in the table
• Steps for the ripple tank method:

  • Pour water to a depth of about 5 mm into the tank
  • Adjust the height of the wooden rod so that it just touches the surface of the water
  • Switch on the overhead lamp and the electric motor
  • Adjust the speed of the motor to produce low frequency water waves
  • Adjust the height of the lamp so that the pattern of the waves can be clearly seen on the white card
  • Place a metre ruler at right angles to the waves shown in the pattern on the card
  • Use the ruler to measure across as many waves as you can. Then divide that length by the number of waves giving the wavelength
• To find the frequency of the waves:

  • Count the number of waves passing a point in 20 seconds using a stop clock
  • Divide the number of waves counted by 20 to get the frequency of the waves
  • Record the frequency value in the table
• To calculate the speed of the waves:

  • Use the equation: wave speed = frequency × wavelength
• Sound waves can travel through solids causing vibrations in the solid
• Normal human hearing is from 20Hz to 20,000Hz
• When the tuning fork is placed against an eardrum, the sound produced travels along the bones of the middle ear and causes the eardrum to vibrate. This sets up a series of compressions and rarefactions in the air inside the cochlea which stimulate the hair cells lining the inner ear. The brain interprets these signals as sound.
• The pitch of a sound depends on its frequency
• The loudness of a sound depends on its amplitude (or intensity)
• A reflected sound wave is an echo
• Ultrasound waves have a frequency higher than the upper limit of hearing for humans
• Ultrasound waves are partially reflected when they meet a boundary between two different media
• Ultrasound waves are used for medical and industrial imaging
• Ultrasound is safer than X-ray because ultrasound does not cause mutations or increase the risk of cancer
• the two main types of seismic waves are P-waves and S-waves
• P-waves are longitudinal waves that travel through solids and liquids.
• S-waves are transverse waves that travel through only solids (cannot travel through liquids)