waves for detection and exploration

• ultrasonic waves have a frequency greater than 20khz
• when an ultrasonic wave meets a boundary between two different mediums it is partially reflected
• echo sounding or sonar is the use of ultrasonic waves for detecting obects in deep water or depth
• the speed is the speed of sound in water which is 1500 m/s
• two types of seismic waves

  • p-waves
  • s-waves
• p-waves

  • longitudinal
  • travel at the speed of sound , twice as fast as s-waves
  • travels at different speeds through solids and liquids
• when seismic waves are produces , the difference in time between the arrival in pwaves and swaves at detectors ca provide evidence of the earth structure
• during an earthquake

  • seismic waves travel out wards in a curved path due to the earths increasing density and depth
• p-waves shadow zone (longitudinal)

  • they are able to travel through the liquid outer core
  • however , they are refracted at the boundary between the semi-solid mantle and liquid outer core
  • then they are refracted again at the liquid outer core and solid inner core
  • these shadow zones are used to determine the size and composition of the inner and outer core
• s-wave shadow zones (transverse)

  • not able to travel through the liquid outer core
  • this results in a large shadow zone opposite where the earthquake took place
  • the shadow zone provides evidence for the size of the earths core
• uses of ultrasound

  • detecting defects im material
  • medicine like pre-natal scanning
• s-waves

  • transverse waves
  • not able to transverse through liquids