chapter 12

• transverse waves = direction of oscillations are perpendicular to the direction of energy transfer
• longitudinal waves = direction of oscillations are parallel to direction of energy transfer
• mechanical waves = a medium must travel though it

  • sound waves , seismic waves
• reflection = when waves bounce back
• refreaction = when aves change speed and direction as they cross the boundary
• example of transverse wave = electromagnetic waves
• angle of incidence = angle of reflection
• ultrasound waves = sound waves with a frequency higher than range of human hearing (>20,000Hz)
• when waves move between mediums of different densities, they refract
• seismic waves help to see the structure of the Earth
• how to measure wave speed (practical):

  • measure distance between two points
  • measure time for waves to travel between points with stop watch
  • calculate speed = distance / time
  • more accuracy by filming a wave and slow down the video
• waves transfer : energy and information
• waves do not transfer : matter
• frequency = number of waves passing a point per second (Hz)
• time period = time for one wave to complete a wave oscillation
• secondary waves = transverse and are slow
• primary waves = longitudinal and are fast
• primary waves can pass through the earths outer core