Ultrasound

Ultrasound

1. The human ear can detect sound waves with frequencies between 20Hz and 20,000Hz.

   • Sound waves with a frequency higher than this are called ULTRASOUND WAVES

2. Electronic systems can be used to produce ultrasound waves

   • When a wave meets a boundary between two different materials, part of the wave is reflected
     • The wave travels back through the material to a detector. The time it takes to reach the detector can be used to calculate how far away the boundary is
       • The results may be processed by a computer to give an image

3. The distance between an ultrasound pulse can be calculated using the equation: s = v x t

   • s = the distance travelled in metres, m
   • v = speed of the ultrasound wave in metres per second m/s
   • t = time taken in seconds, s

4. In the time between a transmitter sending out a pulse of ultrasound and it returning to a detector, it has travelled from the transmitter to the boundary and back (i.e. twice the distance to the boundary)

5. It can be used in medicine for scanning

   • It is non-ionising so is safer to use than X-rays
     • It can be used for scanning unborn babies and soft tissue such as the eye.
   • It may also be used in therapy, for example to shatter kidney stones into small pieces