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Correct Answer: A
Correct Answer: A
Method / Topic: Physics
The correct option matches the required rule and the given information.
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Correct Answer: A
Method / Topic: Physics
When a sound wave encounters a boundary between tissues with different acoustic impedances, part of its energy is reflected. The returning echo is detected by the probe and used to determine the depth and properties of internal structures. This result follows from the stated physical model and consistent SI units. For MCAT physics, first identify the system, list known quantities, and choose the governing relationship before substituting numbers. Track direction, signs, exponents, and unit conversions; then test whether the magnitude is physically reasonable. Common distractors omit a round trip, confuse radius with area, ignore an inverse-square or fourth-power dependence, use peak instead of average behavior, or mix stored energy with dissipated power. In clinical and laboratory settings, the same
helps interpret imaging depth, fluid flow, electrical discharge, forces, and energy safely. A final dimensional check should reproduce the unit requested in the
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PASSAGE 4 — DIAGNOSTIC ULTRASOUND An ultrasound probe emits a 5.0 MHz wave into soft tissue where sound travels at 1500 m/s. A boundary lies 3.0 cm below the skin. Part of the pulse reflects and returns to the probe. The acoustic intensity reflection coefficient at a boundary is R = [(Z₂ − Z₁)/(Z₂ + Z₁)]², where Z is acoustic impedance. Neglect attenuation. QUESTION 10: What physical phenomenon allows part of the ultrasound pulse to return to the probe?
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Correct Answer: A
Method / Topic: Physics
The correct option matches the required rule and the given information.
Short Explanation
Detailed Explanation
Correct Answer: A
Method / Topic: Physics
When a sound wave encounters a boundary between tissues with different acoustic impedances, part of its energy is reflected. The returning echo is detected by the probe and used to determine the depth and properties of internal structures. This result follows from the stated physical model and consistent SI units. For MCAT physics, first identify the system, list known quantities, and choose the governing relationship before substituting numbers. Track direction, signs, exponents, and unit conversions; then test whether the magnitude is physically reasonable. Common distractors omit a round trip, confuse radius with area, ignore an inverse-square or fourth-power dependence, use peak instead of average behavior, or mix stored energy with dissipated power. In clinical and laboratory settings, the same
helps interpret imaging depth, fluid flow, electrical discharge, forces, and energy safely. A final dimensional check should reproduce the unit requested in the
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