Question:
Which of the following statement(s) about ultrasound waves is/are true?
Which of the following statement(s) about ultrasound waves is/are true?
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When studying ultrasound waves, focus on the concepts of acoustic impedance and reflection/transmission coefficients, as they determine how sound waves interact with biological tissues.
Updated On: Apr 14, 2025
- Acoustic impedance of biological tissues is directly proportional to its density
- The reflection coefficient depends on the impedance mismatch at the interface of two biological tissues
- The transmission coefficient is independent of the impedance of biological tissues
- Biological tissues do not reflect ultrasound waves
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The Correct Option is A, B
Solution and Explanation
(A) Acoustic impedance of biological tissues is directly proportional to its density
This statement is true. The acoustic impedance (\(Z\)) of a material is given by the product of the density of the material and the speed of sound in it. Therefore, the acoustic impedance is directly proportional to the density of biological tissues.
\[ Z = \rho v \] where \( \rho \) is the density and \( v \) is the speed of sound in the medium.
(B) The reflection coefficient depends on the impedance mismatch at the interface of two biological tissues
This statement is true. The reflection coefficient (\(R\)) is determined by the impedance mismatch between two tissues. The greater the difference in acoustic impedance between the two tissues, the greater the reflection.
\[ R = \left( \frac{Z_2 - Z_1}{Z_2 + Z_1} \right)^2 \] where \(Z_1\) and \(Z_2\) are the acoustic impedances of the two tissues.
(C) The transmission coefficient is independent of the impedance of biological tissues
This statement is false. The transmission coefficient is indeed dependent on the impedance mismatch between two tissues. A large impedance mismatch leads to more reflection and less transmission.
(D) Biological tissues do not reflect ultrasound waves
This statement is false. Biological tissues do reflect ultrasound waves to some extent, depending on the difference in acoustic impedance between the tissues.
This statement is true. The acoustic impedance (\(Z\)) of a material is given by the product of the density of the material and the speed of sound in it. Therefore, the acoustic impedance is directly proportional to the density of biological tissues.
\[ Z = \rho v \] where \( \rho \) is the density and \( v \) is the speed of sound in the medium.
(B) The reflection coefficient depends on the impedance mismatch at the interface of two biological tissues
This statement is true. The reflection coefficient (\(R\)) is determined by the impedance mismatch between two tissues. The greater the difference in acoustic impedance between the two tissues, the greater the reflection.
\[ R = \left( \frac{Z_2 - Z_1}{Z_2 + Z_1} \right)^2 \] where \(Z_1\) and \(Z_2\) are the acoustic impedances of the two tissues.
(C) The transmission coefficient is independent of the impedance of biological tissues
This statement is false. The transmission coefficient is indeed dependent on the impedance mismatch between two tissues. A large impedance mismatch leads to more reflection and less transmission.
(D) Biological tissues do not reflect ultrasound waves
This statement is false. Biological tissues do reflect ultrasound waves to some extent, depending on the difference in acoustic impedance between the tissues.
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