Waves

• Example of transverse waves.

  1. Ripples on the surface of water.
• Example of longitudinal waves.

  1. Sound waves travelling in the air.
• All waves transfer energy from one place to another.
• What type of energy do ripples transfer?

  Kinetic
• What type of energy do sound waves transfer?

  Sound energy.
• What are oscillations?


  The movement of a wave up and down.
• In transverse waves oscillations are perpendicular to the direction of energy transfer.
• What are compressions?


  Regions where the air particles are close together.
• What are rarefactions?


  Area between compressions where air particles are spread out.
• In longitudinal waves the oscillations are parallel to the direction of energy transfer.
• One difference between transverse and longitudinal waves.

  1.Longitudinal waves require a medium to travel in the air.

  2. Not all transverse waves require a medium
• What is amplitude?


  The maximum displacement of a point on a wave away from its undisturbed position.
• What is wavelength?


  The distance from a point on one wave to the equivalent point on the adjacent wave.
• What is frequency?


  Number of waves passing a point each second.
• What is the unit for frequency?

  Hertz.
• What is a period?

  Time taken in seconds for one wave to pass a point.
• What is wave speed?

  The speed at which the wave moves through the medium.
• What happens when a wave hits a boundary with a different material?

  1. Reflection.
  2. Refraction.
  3. absorb.
• Angle of incidence = angle of reflection.
• Sound is a longitudinal wave.
• What do sound waves in the air trigger?

  Vibrations in solids.
• What is the range of human hearing?

  20 Hz to 20,000 Hz.
• What happens when waves move from one medium to another?

  Their speed can change.
• What doesn't change when a wave changes medium?


  Frequency.
• How can we view features of a sound wave?

  By connecting a microphone to a cathode ray oscilloscope.
• What is a problem with a cathode ray oscilloscope?

  They represent sound waves as if they were transverse waves but sound waves are longitudinal.
• A high frequency sound has a high pitch.
• A low frequency sound has a low pitch.
• A small amplitude has a quiet sound.
• A large amplitude has a loud sound.
• Sound waves can only move through a medium.
• Why can sound waves only move through a medium?

  Because sound waves move by particles vibrating.
• Why can't sound waves pass through a vacuum?

  There are no particles.
• What do we call a reflected sound wave?

  Echo.
• What is ultrasound?


  Sound waves with a frequency higher than the upper limit of human hearing.
• The frequency of ultrasound is atleast 20,000 Hz.
• Key feature of ultrasound.

  Partially reflects at the boundary between two different densities.
• What can ultrasound scanners produce?

  Images of internal organs such as the kidney or heart or a foetus.
• Why is ultrasound safer than x - rays?

  Ultrasound doesn't cause mutations or an increased risk of cancer.
• Ultrasound is also used in industrial imaging.