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Ultrasounds
- The human ear can detect sound
waves with frequencies between
20Hz and 20 000 Hz.
- Sound waves of a higher
frequency than this are
called ultrasound waves/
- Sound waves of a higher
frequency than this are
called ultrasound waves/
- 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 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.
- When a wave meets a
boundary between two
different materials, part of
the wave is reflected.
- The distance travelled by an ultrasound pulse can
be calculated using the equation:
- S = V x T
- S is the distance travelled in
metres, m
- V is the speed of the ultrasound wave in
metres per second, m/s.
- T is the time taken in
seconds, s
- S is the distance travelled in
metres, m
- S = V x T
- 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 a boundary and back,i.e twice the distance to the
boundary.
- Ultrasounds 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. Ultrasound may be used in therapy, for example to shatter kidney stones
into small pieces.
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