ARDMS SPI EXAM: 300 MULTIPLE CHOICE QUESTIONS
WITH ANSWERS AND RATIONALES
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Domain 1: Sound Waves and Propagation (Questions 1-60)
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Question 1
What is the frequency of a sound wave if its period is 0.5 microseconds?
A) 1 MHz
B) 2 MHz
C) 5 MHz
D) 10 MHz
Correct Answer: B) 2 MHz
Rationale: Frequency (f) is the reciprocal of period (T). f = 1/T = 1/0.5 μs = 2 MHz.
As frequency increases, period decreases proportionally. This inverse relationship
is fundamental to understanding ultrasound physics and transducer selection .
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Question 2
Which acoustic variable is defined as the concentration of mass per unit volume?
A) Pressure
B) Density
C) Particle motion
D) Acoustic impedance
Correct Answer: B) Density
Rationale: Density is the mass per unit volume of a medium (kg/m³). Along with
pressure and particle motion, density is one of the three acoustic variables that
describe sound wave propagation through a medium .
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Question 3
A sound wave travels through soft tissue at 1,540 m/s. If the frequency is 5 MHz,
what is the wavelength?
A) 0.154 mm
B) 0.308 mm
,C) 0.616 mm
D) 1.54 mm
Correct Answer: B) 0.308 mm
Rationale: Wavelength (λ) = propagation speed / frequency. λ = 1,540 m/s /
5,000,000 Hz = 0.000308 m = 0.308 mm. Wavelength determines axial resolution;
shorter wavelengths provide better resolution .
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Question 4
When a sound wave travels from one medium to another with a different acoustic
impedance, what determines the amount of reflection?
A) The frequency of the sound wave
B) The angle of incidence only
C) The difference in acoustic impedance
D) The propagation speed only
Correct Answer: C) The difference in acoustic impedance
Rationale: Reflection at an interface is determined by the acoustic impedance
mismatch between the two media. The greater the impedance difference, the
, more sound energy is reflected. This is described by the reflection coefficient
equation .
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Question 5
What is the acoustic impedance of a medium with a density of 1,060 kg/m³ and a
propagation speed of 1,540 m/s?
A) 1.45 × 10⁵ Rayls
B) 1.63 × 10⁶ Rayls
C) 1.45 × 10⁶ Rayls
D) 1.63 × 10⁵ Rayls
Correct Answer: B) 1.63 × 10⁶ Rayls
Rationale: Acoustic impedance (Z) = density × propagation speed. Z = 1,060
kg/m³ × 1,540 m/s = 1,632,400 Rayls ≈ 1.63 × 10⁶ Rayls. Impedance determines
how much sound is reflected at tissue interfaces .
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Question 6
Which of the following wave types has particle motion parallel to the direction of
wave propagation?
WITH ANSWERS AND RATIONALES
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Domain 1: Sound Waves and Propagation (Questions 1-60)
---
Question 1
What is the frequency of a sound wave if its period is 0.5 microseconds?
A) 1 MHz
B) 2 MHz
C) 5 MHz
D) 10 MHz
Correct Answer: B) 2 MHz
Rationale: Frequency (f) is the reciprocal of period (T). f = 1/T = 1/0.5 μs = 2 MHz.
As frequency increases, period decreases proportionally. This inverse relationship
is fundamental to understanding ultrasound physics and transducer selection .
,---
Question 2
Which acoustic variable is defined as the concentration of mass per unit volume?
A) Pressure
B) Density
C) Particle motion
D) Acoustic impedance
Correct Answer: B) Density
Rationale: Density is the mass per unit volume of a medium (kg/m³). Along with
pressure and particle motion, density is one of the three acoustic variables that
describe sound wave propagation through a medium .
---
Question 3
A sound wave travels through soft tissue at 1,540 m/s. If the frequency is 5 MHz,
what is the wavelength?
A) 0.154 mm
B) 0.308 mm
,C) 0.616 mm
D) 1.54 mm
Correct Answer: B) 0.308 mm
Rationale: Wavelength (λ) = propagation speed / frequency. λ = 1,540 m/s /
5,000,000 Hz = 0.000308 m = 0.308 mm. Wavelength determines axial resolution;
shorter wavelengths provide better resolution .
---
Question 4
When a sound wave travels from one medium to another with a different acoustic
impedance, what determines the amount of reflection?
A) The frequency of the sound wave
B) The angle of incidence only
C) The difference in acoustic impedance
D) The propagation speed only
Correct Answer: C) The difference in acoustic impedance
Rationale: Reflection at an interface is determined by the acoustic impedance
mismatch between the two media. The greater the impedance difference, the
, more sound energy is reflected. This is described by the reflection coefficient
equation .
---
Question 5
What is the acoustic impedance of a medium with a density of 1,060 kg/m³ and a
propagation speed of 1,540 m/s?
A) 1.45 × 10⁵ Rayls
B) 1.63 × 10⁶ Rayls
C) 1.45 × 10⁶ Rayls
D) 1.63 × 10⁵ Rayls
Correct Answer: B) 1.63 × 10⁶ Rayls
Rationale: Acoustic impedance (Z) = density × propagation speed. Z = 1,060
kg/m³ × 1,540 m/s = 1,632,400 Rayls ≈ 1.63 × 10⁶ Rayls. Impedance determines
how much sound is reflected at tissue interfaces .
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Question 6
Which of the following wave types has particle motion parallel to the direction of
wave propagation?
