Waves

• Transverse waves


  Waves where the oscillations are perpendicular to the direction of energy transfer
• Longitudinal waves


  Waves where the oscillations are parallel to the direction of energy transfer
• Transverse waves


  • Ripples on the surface of water
• Longitudinal waves


  • Sound waves traveling in air
• All waves are either transverse or longitudinal
• Wave


  Transfers energy from one place to another
• Ripples transfer kinetic energy
• Sound waves transfer sound energy
• Transverse waves


  • Oscillations are perpendicular to the direction of energy transfer
• Longitudinal waves


  • Oscillations are parallel to the direction of energy transfer
• Longitudinal waves require a medium to travel in (e.g. air, liquid, solid)
• Not all transverse waves require a medium
• In waves, it is the wave that travels, not the medium (e.g. water, air)
• Amplitude


  The maximum displacement of a point on a wave away from its undisturbed position
• Transverse wave


  • Amplitude is easier to label on
• Wavelength


  The distance from a point on one wave to the equivalent point on the adjacent wave
• Wavelength symbol


  Greek letter lambda (λ)
• Frequency


  The number of waves passing a point each second
• Frequency unit


  Hertz (Hz), 1 Hz = 1 wave per second
• Calculating frequency from a diagram


  Count the total number of waves in 1 second
• Period


  The time in seconds for one wave to pass a point
• Calculating period from frequency

  Period (s) = 1 / Frequency (Hz)
• Wave


  A disturbance that transfers energy through a medium or space without the permanent displacement of the particles in the medium
• What happens when a wave hits a boundary with a different material

  1. Transmitted

  2. Absorbed

  3. Reflected
• Waves can change direction when passing from one material to another, this is called refraction
• Reflection of waves


  • Incident ray
  • Normal line
  • Angle of incidence
  • Angle of reflection
• Angle of reflection


  Equals the angle of incidence
• Constructing a ray diagram to show reflection of a wave


  1. Draw incident ray

  2. Draw normal line

  3. Draw reflected ray

  4. Extend reflected rays to find image position
• Sound waves


  Longitudinal waves that can be transmitted from one medium to another
• Sound wave transmission


  1. Air particles vibrate

  2. Vibrations pass to solid medium

  3. Vibrations cause microphone cone to vibrate

  4. Microphone converts vibrations to electrical signals

  5. Sound waves in air cause eardrum to vibrate
• Human hearing range


  • 20 Hertz to 20,000 Hertz
  • Frequencies outside this range may not cause eardrum to vibrate
• Wave equation


  Wave speed = frequency x wavelength
• Frequency does not change when a wave changes medium</b>
• Wave speed changes when wave passes from one medium to another

  Wavelength also changes
• Cathode ray oscilloscope


  Represents sound waves as transverse waves, but sound waves are actually longitudinal
• High frequency sound


  • High pitch
• Low frequency sound


  • Low pitch
• High amplitude sound


  • Loud
• Low amplitude sound


  • Quiet
• Sound waves can only move through a medium (e.g. air, solid)