Ultrasound waves

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  • Ultrasound
    • ultrasound was have a higher frequency than what people can hear
      • have a wavelength of 1mm- low res
    • producing ultrasound
      • piezoelectric crystals
        • when a pd is applied across the crystals they mechanically deform- producing a pd
        • used in transducers
          • generate ultrasound pulses of a specific frequency
          • to detect reurning echos of ultrasound waves
      • transducers
        • a.c current applied and causes forced vibrations
        • frequency of the vibrations = F of P.D
        • amplitude at its  max when frequency = natural frequency of the crystal
          • emits ultrasound waves
            • damping material used for pulses
    • ultrasound reflection
      • when pulses reach an interface
        • size of echo depends on material and  properties
      • acoustic impedance = velocity x density
        • greater the diff = greater echo


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