waves

• waves transfer energy from one place to another without transferring matter, by causing the particles in a medium to vibrate.
• Transverse wave:

  • Waves where the vibrations are perpendicular to the direction of energy transfer.
  • Can travel through a vacuum.
  • Transfer energy
• Crest (peak)


  The highest point of a wave.
• Trough


  The lowest point of a wave.
• Displacement


  How far a point on the wave has moved from its rest position.

  measured in: metres (m)
• Amplitude


  The maximum displacement of a point on a wave away from its rest position. On a diagram it's the height from the rest position (the middle line of the wave) to the crest.

  measured in: Metres (m)
• Examples of transverse waves:

  • Electromagnetic waves (visible light)
  • Water waves
  • Seismic waves (S-waves)
• Longitudinal waves


  • Waves where the vibrations are parallel to the direction of energy transfer, causing areas of compression and rarefraction.
  • Needs particles to travel.
• Longitudinal waves:

  A) rarefaction

  B) compression

  C) one complete wave

  D) wavelength

  
• Compression


  The area, in a longitudinal wave, where the particles are closest together.
• Rarefaction


  An area, in a longitudinal wave, where the particles are furthest apart.
• examples of longitudinal waves:

  • Sound waves
  • seismic waves (P-wave)
• Oscillations


  vibrations
• Sound waves in air:

  • The sound you hear is the result of waves travelling to your ears.
  • The air molecules VIBRATE BACK AND FORTH as the sound wave passes but do NOT travel to you.
  • If the air travelled with the sound, you would feel a constant wind, when it was producing sound, which we do not.
  • if we use smoke, we can see that while the smoke or feather may flutter due to the vibrations, they do NOT move towards us with the sound.

  
• Compression


  Squeezing together
• frequency


  The number of waves that pass a certain point in one second.

  • Measured in hertz (Hz)
• Period (time period)


  The time it takes for one complete wave to pass a point

  • measured in seconds (s)
• wave speed


  The speed at which energy is transferred (or the wave moves) through a medium.
• The equation to work out wave speed:

  A) frequency

  B) wavelength

  
• Longitudinal waves:

  • oscillations are parallel to the direction of energy transfer causing areas of rarefaction and compression.
  • Transfers energy
  • Can be heard
  • Needs a medium to travel
• Amplitude - on a diagram


  The height of a wave crest or trough of a transverse wave.
• Wavelength


  The distance between a point on one wave and the same point on the next wave.

  • Represented by: Greek letter 'lambda' (λ)
  • Measured in: metres (m)
• how is a water wave with a speed of 0.22m/s, compare to the typical speed of a person walking?

  The typical walking speed = 1.5m/s, so the water waves are slower.
• Explain how the depth of the water affects the wavelength of the wave if the frequency is constant.

  Deeper water means longer wavelength because v increases and f is constant.
• waves are produced by a disturbance.
• transverse waves:

  A) displacement

  B) amplitude

  C) one complete wave

  D) crest

  E) wavelength

  F) trough

  G) wavelength

  H) rest position

  I) distance