Ultrasound

• • Ultrasound is sounds with frequency higher than 20,000 Hz
• • When ultrasound travels from one body to another, it can be absorbed
  • When a wave passes from one medium to another, part of the wave is reflected off the boundary between two media and some is transmitted
  • The time taken for the reflections to reach a detector can be used to measure the distance of the boundary
• MEDICAL IMAGING:

  • When ultrasound reaches boundary between two different media (e.g fluid in womb and skin of foetus), some of the wave is reflected back and detected
  • The exact timing of these echoes are processed by a computer to produce video image of foetus
  • X rays are not used as they are types of ionising radiation, which is harmful
• INDUSTRIAL IMAGING:

  • Ultrasound can be used to find flaws in materials
  • Ultrasound waves entering a material will be reflected by the far side of the material
  • If there is a flaw, like a crack, the wave will be reflected earlier
• Ultrasound thickness equation

  1/2 x v x t