Physics A-Level
Coupling gel
What Coupling gel means in Physics A-Level, as defined for AQA, OCR.
Definitions of Coupling gel
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Reference: OCR
Needed in scanning because at a soft-tissue–air boundary Z₂ is much smaller than Z₁, so the fraction reflected is close to 1; the gel improves transmission.
Used because it has an impedance close to that of skin, reducing reflection at the skin–air boundary.
Topics that use Coupling gel
- Ultrasound imaging (A-level only) (AQA A-Level)
- Using ultrasound (OCR A-Level)
Related terms
- A-scan
- Acoustic impedance
- B-scan
- Intensity reflection coefficient
- Piezoelectric effect
- Acoustic impedance and reflection
- Acoustic impedance mismatch
- Acoustic matching
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