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Quizzes > Science > Physics

Take the Ultrasound Physics Quiz: Test Your Vocabulary & Units Knowledge!

Think you can ace ultrasound physics vocabulary and unit relationships? Start the quiz now!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art style ultrasound probe emitting waveforms next to floating letters units and symbols on coral background

Ready to challenge yourself with our free ultrasound physics quiz on units & terms? This interactive ultrasound physics quiz is designed to test your mastery of ultrasound physics vocabulary, from sound wave characteristics to key medical imaging terms. You'll explore ultrasound units relationships through engaging scenarios and tackle an acoustic impedance quiz segment to see how well you grasp these core concepts. Expand your understanding of frequency intensity test parameters as you progress, ensuring you can confidently apply these principles in real-world contexts. Whether you're reviewing after a foundation class like physics unit one or brushing up on sound fundamentals , you'll find this quiz both informative and rewarding. Jump in now to boost your skills, satisfy your curiosity, and start the quiz today!

What is the standard SI unit for frequency in ultrasound physics?
Pascal (Pa)
Rayl
Hertz (Hz)
Meter (m)
Frequency measures cycles per second and its SI unit is the hertz, symbolized as Hz. This is universally used in ultrasound to specify the oscillation rate of sound waves. Other units like pascal measure pressure and rayl measure acoustic impedance. Hertz
Which unit is commonly used to express the wavelength of an ultrasound wave in soft tissue?
Watts (W)
Millimeters (mm)
Candela (cd)
Kelvin (K)
Wavelength in medical ultrasound is typically on the order of fractions of a millimeter and is expressed in millimeters. Other units like watts measure power and kelvin measure temperature. Wavelength
How are frequency (f) and period (T) mathematically related?
f = 2?/T
T = 1 / f
T = f  ×  2
f = T^2
Period is the reciprocal of frequency, meaning T = 1/f. This relationship holds for all periodic wave phenomena, including ultrasound. Period and Frequency
What is the approximate propagation speed of ultrasound in soft tissue?
1540 m/s
3400 m/s
0.154 m/s
300 m/s
The average speed of sound in soft tissue is about 1540 meters per second. This value is used in distance calculations for ultrasound imaging. Speed of Sound
Which unit best describes ultrasound intensity?
Rayl
Watts per square centimeter (W/cm²)
Decibels (dB)
Pascal-second (Pa·s)
Intensity is power per unit area and is expressed in W/cm² in ultrasound physics. Rayl is the unit of acoustic impedance, and decibels measure relative changes. Intensity
Attenuation in ultrasound refers to:
Change in frequency during propagation
Reflection at tissue interfaces
Increase in speed with depth
Decrease in amplitude or intensity with distance
Attenuation describes the reduction in wave amplitude and intensity as it travels through tissue due to absorption and scattering. It does not describe reflections or frequency shifts. Ultrasound Attenuation
Which unit is used for the attenuation coefficient in diagnostic ultrasound?
Decibels per centimeter (dB/cm)
Rayl/m
Watts per meter (W/m)
Hertz (Hz)
The attenuation coefficient quantifies loss in dB per unit depth, so it's expressed in dB/cm. Other units describe frequency or power. Attenuation Coefficient
What is the pulse repetition frequency (PRF) measured in?
Hertz (Hz)
Rayl (kg/m²·s)
Centimeters (cm)
Seconds (s)
PRF is the number of pulses emitted per second, so it is measured in hertz. It is not a distance or impedance measure. Repetition Rate
The pulse repetition period (PRP) is:
The depth resolution of the system
The time between the start of successive pulses
The number of pulses per second
The spatial length of a pulse
PRP is defined as the time interval from the start of one pulse to the start of the next. It complements PRF. Pulse Repetition Period
Duty factor describes:
The speed variation in tissue
The beam width at focus
The ratio of reflected to transmitted intensity
The fraction of time that the ultrasound is actively transmitting
Duty factor is the percentage of time that pulses are present (pulse duration divided by PRP). It does not describe reflections or beam geometry. Ultrasound Basics
Which prefix denotes one million times in ultrasound frequency labels?
Mega (M)
Micro (?)
Kilo (k)
Milli (m)
The prefix 'mega' represents 10?, so MHz means one million hertz. Kilo is 10³ and milli is 10?³. Metric Prefix
Which of the following best describes acoustic impedance?
The product of tissue density and sound speed
The time delay between pulses
The width of the ultrasound beam
The ratio of reflected to incident intensity
Acoustic impedance (Z) equals density (?) times propagation speed (c). It determines reflection at boundaries. Acoustic Impedance
How do you calculate wavelength (?) in soft tissue given frequency (f) and speed (c)?
? = f / c
? = 1 / (c·f)
? = c / f
? = c × f
Wavelength equals propagation speed divided by frequency. This formula is fundamental for ultrasound resolution calculations. Wavelength
Which unit represents acoustic impedance in ultrasound?
Tesla (T)
Rayl (kg/m²·s)
Siemens (S)
Decibel (dB)
The rayl, with units kg/(m²·s), is the SI unit of acoustic impedance. Decibels measure relative intensity. Acoustic Impedance
A 6 dB increase in intensity corresponds to a:
Twofold increase in intensity
No change in intensity
Fourfold increase in intensity
Tenfold increase in intensity
Every 3 dB doubles intensity; thus, a 6 dB increase is a fourfold change. This logarithmic relationship is key in ultrasound gain settings. Decibel
If the ultrasound amplitude doubles, by how many decibels does it change?
0 dB
3 dB
6 dB
10 dB
Amplitude changes in dB are given by 20·log10(A?/A?). Doubling amplitude yields 20·log10(2) ? 6 dB. Decibel
Axial resolution improves when the spatial pulse length:
Exceeds beam width
Remains constant
Increases
Decreases
Axial resolution equals half the spatial pulse length, so shorter pulses yield better resolution. Longer pulses degrade it. Axial Resolution
Lateral resolution in ultrasound imaging is primarily determined by:
Attenuation rate
Pulse duration
Beam width
Frequency only
Lateral resolution is set by the beam diameter; narrower beams resolve two structures side by side more clearly. Pulse duration affects axial resolution. Ultrasound Spatial Resolution
Duty factor (DF) is computed as:
Pulse repetition period ÷ pulse duration
Pulse repetition frequency × pulse duration
Pulse duration ÷ pulse repetition period
Pulse duration × number of cycles
Duty factor is the fraction of time the system transmits pulses, calculated as PD/PRP. It's unitless. Duty Cycle
The bandwidth of an ultrasound transducer is defined as:
Central frequency squared
Wavelength range in tissue
Pulse repetition frequency range
Difference between highest and lowest frequencies it can emit
Bandwidth is the range of frequencies over which the transducer is efficient, equal to f_high - f_low. Wide bandwidth produces short pulses. Bandwidth
Q-factor of a transducer is the ratio of:
Wavelength to beam width
Acoustic impedance to density
Pulse duration to PRP
Resonant frequency to bandwidth
Q-factor equals the center (resonant) frequency divided by the bandwidth. High Q means narrow bandwidth. Q Factor
The near field (Fresnel zone) of a transducer is:
A region unaffected by attenuation
Where frequency doubles
The region from face to focus where beam is converging
The region beyond focus where beam diverges
The near field extends from the transducer face to the natural focus, with constructive interference narrowing the beam. Further out is the far field. Fresnel Zone
Beam divergence angle depends on which of the following?
PRF and PRP
Aperture size and wavelength
Attenuation coefficient
Acoustic impedance and density
Divergence angle ? ? ?/D, where ? is wavelength and D is aperture diameter. Larger apertures and higher frequencies (smaller ?) reduce divergence. Diffraction Limited System
If a pulse duration is 2 ?s and the ultrasound frequency is 2 MHz, how many cycles are in the pulse?
1 cycle
8 cycles
4 cycles
2 cycles
Period T = 1/f = 0.5 ?s; dividing PD (2 ?s) by T yields 4 cycles. This shows how cycle count relates to pulse length. Cycle (Physics)
What is the approximate maximum PRF when imaging to a depth of 15 cm?
50 Hz
5 kHz
50 kHz
500 Hz
Max PRF ? c/(2·depth) = 1540 m/s ÷ (2·0.15 m) ? 5133 Hz (~5 kHz). This ensures echoes return before next pulse. Ultrasound Physics
Given a spatial pulse length (SPL) of 0.8 mm, what is the axial resolution?
0.8 mm
0.2 mm
1.6 mm
0.4 mm
Axial resolution = SPL/2, so 0.8 mm ÷ 2 = 0.4 mm. This determines the minimum separable distance along the beam axis. Axial Resolution
What is the half-value layer (HVL) in ultrasound?
Thickness that doubles power
Depth at which intensity is reduced by 3 dB
Depth at which amplitude doubles
Distance traveled in one pulse
HVL is the thickness required to reduce intensity by half, which is a 3 dB loss. It indicates tissue attenuation properties. Half-Value Layer
If the attenuation coefficient is 0.5 dB/cm/MHz, frequency is 5 MHz, and path length is 4 cm, total attenuation is:
20 dB
2.5 dB
0.5 dB
10 dB
Total attenuation = coefficient × frequency × distance = 0.5 × 5 × 4 = 10 dB. This linear relation applies in soft tissue. Attenuation
The relationship between intensity (I) and amplitude (A) is:
I ? A
I ? 1/A
I ? ?A
I ? A²
Intensity is proportional to the square of pressure amplitude in a wave. Doubling amplitude quadruples intensity. Intensity
How is spatial pulse length (SPL) calculated?
Amplitude × duty factor
Speed × PRP
Number of cycles × wavelength
Frequency × period
SPL equals the number of cycles in the pulse multiplied by the wavelength. It influences axial resolution. Wavelength
A high Q-factor transducer has:
Wide bandwidth
Narrow bandwidth
Longer pulse length
Lower center frequency
Q-factor = resonant frequency/bandwidth; high Q indicates a small bandwidth relative to center frequency. Q Factor
When acoustic impedance mismatch increases between two tissues, reflection:
Decreases
Becomes negative
Remains zero
Increases
Reflection coefficient increases with greater impedance mismatch, producing stronger echoes. Reflection Coefficient
Snell's law in ultrasound relates the sine of incident and transmitted angles to:
Attenuation coefficients
Frequency change
Acoustic impedance only
Sound speed in each medium
Snell's law: sin??/sin?? = c?/c?, where c is propagation speed in each medium. It's key in refraction. Snell's Law
What is the wavelength in soft tissue (c=1540 m/s) for a 3.5 MHz ultrasound wave?
1.54 mm
0.044 mm
0.44 mm
4.4 mm
Wavelength ? = c/f = 1540 m/s ÷ 3.5×10? Hz ? 0.00044 m (0.44 mm). Accurate calculation is vital in resolution estimates. Wavelength
Calculate the intensity reflection coefficient between soft tissue (Z?=1.63×10? rayl) and bone (Z?=7.8×10? rayl):
?0.80
?0.01
?0.10
?0.43
R = ((Z??Z?)/(Z?+Z?))² = (6.17/9.43)² ?0.43. This predicts echo strength at interfaces. Reflection Coefficient
A pulse has 5 cycles at 4 MHz in soft tissue. What is the spatial pulse length (SPL)?
5 mm
4 MHz·5 cycles
1.925 mm
0.385 mm
? = 1540/4×10? ?0.385 mm, SPL = 5×0.385 mm ?1.925 mm. This impacts depth resolution. Wavelength
Given an attenuation coefficient ? = 0.75 dB/cm/MHz, frequency 7 MHz, what is the half-value layer (HVL) thickness in cm?
14 cm
0.57 cm
3 cm
7 cm
HVL = 3 dB ÷ (?·f) = 3 ÷ (0.75×7) ?0.571 cm. HVL indicates depth for 50% intensity loss. Half-Value Layer
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Study Outcomes

  1. Identify Key Ultrasound Physics Vocabulary -

    Recognize and define essential terms used in ultrasound physics, ensuring clear understanding of fundamental concepts and language.

  2. Interpret Measurement Units in Ultrasound Physics -

    Analyze common units for frequency, intensity, and acoustic impedance to accurately describe and compare ultrasound parameters.

  3. Explain Relationships Between Frequency, Intensity, and Acoustic Impedance -

    Articulate how changes in frequency affect intensity and acoustic impedance, highlighting their interdependent nature in ultrasound physics.

  4. Calculate Acoustic Impedance and Related Parameters -

    Perform basic calculations involving acoustic impedance, density, and sound speed to solve ultrasound units relationships problems.

  5. Apply Ultrasound Units Relationships in Problem-Solving -

    Use knowledge gained from the ultrasound physics quiz to tackle real-world scenarios, enhancing diagnostic accuracy and confidence.

Cheat Sheet

  1. Frequency - Wavelength Relationship -

    Ultrasound wavelength (λ) and frequency (f) are inversely related by λ = c/f, where c (~1540 m/s in soft tissue) is sound speed. For instance, a 2 MHz probe yields λ≈0.77 mm, improving resolution. Remember: "Higher frequency, shorter lambda."

  2. Acoustic Impedance -

    Acoustic impedance (Z) equals tissue density (ϝ) times sound speed (c): Z=ϝ×c (Rayl). Soft tissue is ~1.63 MRayl, while bone is ~7.8 MRayl, explaining reflection at interfaces. Think "Z stops here" to recall impedance mismatches cause echoes.

  3. Intensity and Power Density -

    Intensity (I) is power (P) per unit area (A): I=P/A, typically expressed in W/cm². Diagnostic imaging uses intensities <0.3 W/cm² to ensure safety. Visualize power spread over the beam area to gauge bioeffects.

  4. Attenuation Coefficient -

    Attenuation α≈0.5 dB/cm/MHz in soft tissue, meaning energy loss increases with depth and frequency. A 5 MHz beam loses ~2.5 dB per cm. Mnemonic: "Half-dB per cm per MHz" for rapid recall.

  5. Resolution vs. Penetration Trade-Off -

    Axial resolution equals λ/2, so higher frequencies (shorter λ) yield finer detail but shallower penetration. A 10 MHz probe gives axial resolution ~0.08 mm but is limited at depth. Balance frequency choice based on target anatomy.

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