ALL ABOUT WAVES: SOUND, AND DOPPLER EFFECT

• Wave

  Disturbance that propagates from one place to another
• Types of waves

  • Mechanical waves
  • Electromagnetic waves
• Mechanical waves

  • Longitudinal motion of wave and particles that are parallel
• Electromagnetic waves

  • Transverse motion of waves and particles that are perpendicular
• Mechanical waves (sound waves)

  • Needs a medium to travel (all states of matter, but never in a vacuum)
• Electromagnetic waves (infrared waves)

  • Does not need a medium to travel (vacuum, but never in all states of matter)
• Sound waves

  • Is a mechanical wave
  • Sound is produced by vibrations
  • Sound can be refracted and reflected
• Sound wave transmission

  Transmitted from one place, to another by the vibration of particles of the medium
• Sound wave's frequency does not change when its waves travel through different mediums
• Longitudinal waves

  Usually produced by pulling and pushing the material or medium, alternating compressions and rarefactions are observed
• Wavelength

  Refers to the distance between two consecutive peaks or troughs of the wave
• Crest

  Highest point
• Trough

  Lowest point
• Frequency

  • Refers to the number of wavelengths passing a certain point per second
  • Measured in hertz (Hz)
• Lambda

  • Indicates the wavelength of a sound wave
  • Measured in meters
• Amplitude

  Distance of maximum peak from its equilibrium point
• Pitch

  Refers to the highness or lowness of a sound
• Intensity

  Amount of energy passing through a space in one second
• Saying "It's loud." is subjective, because for others that certain level of "loudness" may be quiet. More appropriate to use intensity
• Threshold of the human ear

  • 20 Hz to 20,000 Hz
• Infrasound/Subsonic

  Vibrates slowly that the human ear can not hear
• Ultrasound

  Vibrates fast that the human ear can not hear
• Sound travels faster in solids


  Particles are more compact, therefore causing higher collisions (kinetic energy)
• Sound travels very slow in gas


  Particles are not compact
• Factors of the speed of sound

  • Density (less dense)
  • Temperature (hotter)
  • Elasticity (more elastic)
• Higher frequency

  Higher pitch
• Lower frequency

  Lower pitch
• Higher frequency

  Shorter wavelength
• Lower frequency

  Longer wavelength
• Greater the amplitude

  Greater the sound
• Lower the amplitude

  Lower the sound
• Hotter the medium

  Faster the sound travels
• Cooler the medium

  Slower the sound travels
• Greater mass

  Greater density
• intensity of sound

  measured in decibels