sound waves

• What is ultrasound

  • sound above 20khz
  • too high frequency for humans to hear
• How is ultra sound used in sonars

  • detect objects underwater
  • reflected off oceans bottom
  • time take to be recieved is depth of the water
  • distance = 2x depth
• What is infrasound

  • sound with frequencys too low for humans to hear
  • below 20khz
• How is ultrasound used in foetal scanning

  • ultra sound waves pass through the body
  • when met at a boundary (fluid in the womb and skin of foetus) some wave is detected and reflected back
  • distribution of these echos to produce a video image
• How do seismic waves (p and s waves) provide evidence for the earths structure

  • earth quakes produce two types of waves p and s
  • by observing where these properties of waves reflect and refract the properties of earth change dramtically
• What are p waves

  • longtiduinal waves
  • travel through solids and liquids
  • faster than s waves so felt first in an earthquake
• what are s waves

  • travsverse waves
  • slower than p
  • only travel in liquid
  • unable to provide evidence for the earths outer core,showing evidence about its state and size
• What does s waves and p waves curves rell us about the earth

  • when waves travel in curved parts it tells us that the material moving is constantly changing by a new amount
  • when an abrust change it;s changing suddenly by a larger amount
  • this suggest it's entering a new layer of the earths core
• How can sound waves be transferred into vabriations in a solid material

  • Sound waves travel through the air as compressions and rarefactions
  • when they hit a solid the particles in the solid vibrate
  • vibrations can be passed through the solid transferring energy
• Why does sound waves only work over a limit frequency

  • not all frequency can make a solid vibrate as some are reflected or absorbed meaning they don't pass through properly
• Why do sound waves travel faster in night than in day

  • sound waves travel faster In hotter air than cold air
  • difference in temperature causes the wave to refract
  • in night the waves will travell slower in cool air and refract towards the ground
  • sound travels faster as it moves from a more dense medium (cold air) to a less dense medium