Ultrasound | Physics for GCSE/IGCSE - Year 11 PDF Download

Ultrasound

• Humans have a hearing range between 20 Hz and 20,000 Hz, which may decrease with age.
• Ultrasound waves possess frequencies greater than 20,000 Hz.

• Humans perceive sounds within the 20 Hz to 20,000 Hz frequency range. 

Uses of Ultrasound

• When ultrasound encounters a boundary between two different mediums, a portion of the waves is reflected back.
• The remaining waves pass through the material and are transmitted.
• Ultrasound transducers have the capability to both emit and receive ultrasound waves.
  • Emit ultrasound waves
  • Receive ultrasound waves
• The time taken for these reflected waves to reach a detector can be utilized to determine the distance to the boundary. This is achievable because ultrasound travels at varying speeds through different substances.
  • The speed, distance, time equation can be applied to calculate this distance accurately.
    
• Where:
  • Speed (v): measured in meters per second (m/s)
  • Distance (s): measured in meters (m)
  • Time (t): measured in seconds (s)
• Ultrasound waves find applications in both medical and industrial imaging.

Ultrasound in Medicine

• Ultrasound in Medicine:
  • Creates images of a developing fetus in the womb.
  • Generates 2D images of organs and internal structures (excluding bone).
  • Used in medical procedures like kidney stone removal.
• An ultrasound detector consists of a transducer responsible for emitting and receiving ultrasound waves into the body.
• The waves bounce back to the transducer upon encountering tissue boundaries in their path, such as between fluid and soft tissue or between tissue and bone.
• When these echoes reach the transducer, they create electrical signals transmitted to the ultrasound scanner.
• Utilizing the speed of sound and the time taken for each echo to return, the detector calculates the distance from the transducer to the tissue boundary.
• By conducting a series of ultrasound measurements across an area, these time measurements can be used to construct an image.
• The transducer within an ultrasound detector plays a crucial role in producing and receiving ultrasound waves within the body.
• Boundaries between different tissues, like fluid and soft tissue or tissue and bone, are key points where ultrasound waves reflect back to the transducer.
• Ultrasound, unlike many other medical imaging methods, is non-invasive and generally considered safe for imaging purposes.

Ultrasound in Industry

• Ultrasound serves various purposes in industries:
  • Checking for cracks inside metal objects
  • Generating images beneath surfaces
• When a metal block contains a crack, certain waves reflect earlier, appearing as distinct pulses on an oscilloscope trace. Each pulse corresponds to a boundary crossing.
  • Each pulse signifies a wave boundary crossing.
• The constant speed of waves enables the calculation of distance from the source by measuring the time between emission and detection.