Physics Principles

13. Areas of high pressure and density are referred to as: a. Compressions b. Rarefactions c. Condensations d. Rarefractions

13. a. Areas of high pressure and density are referred to as compression.

2. An increase in pulse repetition frequency would lead to: a. An increase in duty factor b. An increase in pulse duration c. An increase in the number of cycles d. A decrease in resolution

a. An increase in pulse repetition period would lead to an increase in duty factor.

38. Damping of the sound beam: a. Reduces the spatial pulse length b. Increases the spatial pulse length c. Increases the pulse duration d. Has no impact on spatial pulse length or pulse duration

a. Damping of the sound beam decreases the spatial pulse length.

21. Density and propagation speed are: a. Inversely related b. Directly related c. Directly proportional d. Unrelated

a. Density and propagation speed are inversely related.

15. Density is typically measured in: a. Kilograms per centimeter cubed b. Millimeters c. Watts per centimeter squared d. Pascals

a. Density is typically measured in kilograms per centimeter cubed.

28. Which of the following is determined by the sound source only? a. Frequency b. Wavelength c. Spatial pulse length d. Propagation speed

a. Frequency is determined by the sound source only.

10. Micro denotes: a. Millionth b. Hundredth c. Million d. Billionth

a. Micro denotes millionth.

22. All of the following are true of power except: a. As amplitude increases, power remains the same b. Power is proportional to amplitude squared c. Intensity is proportional to power d. Power is measured in milliwatts

a. Power decreases as amplitude decreases

32. Which of the following is an appropriate unit of measurement for propagation speed? a. millimeters per microsecond (mm/s) b. watts per centimeter squared (W/cm2) c. microseconds (s) d. kilohertz (kHz)

a. Propagation speed can be measured in millimeters per microsecond.

1. Which of the following is described as the ability of an object to resist compression and relates to the hardness of a medium? a. Stiffness b. Density c. Pressure d. Inertia

a. Stiffness is the ability of an object to resist compression and relates to the hardness of a medium.

9. The attenuation coefficient in soft tissue is equal to: a. One half of the operating frequency b. Double the operating frequency c. Frequency times path length d. The total decibels

a. The attenuation coefficient (in dB/cm) is the rate at which sound is attenuated per unit depth. It is equal to one half of the frequency (f/2) in soft tissue.

40. What is defined as the beginning of one pulse to the beginning of the next pulse, and therefore includes both the "on" and "off" time? a. Pulse repetition period b. Pulse duration c. Duty factor d. Pulse repetition frequency

a. The pulse repetition period is the time from the start of one pulse to the start of the next pulse, and therefore, it includes the "on" (or transmit) and "off" (or listening) times.

29. The prefix "centi" denotes: a. Thousandths b. Hundredths c. Millions d. Hundreds

b. "Centi" denotes hundredths.

33. The major component of attenuation is: a. Scatter b. Absorption c. Transmission d. Refraction

b. Absorption is the major component of attenuation.

18. As imaging depth increases, pulse repetition period: a. Remains constant b. Increases c. Decreases d. Doubles

b. As imaging depth increases, the pulse repetition period increases.

3. Which of the following would have the highest propagation speed? a. Air b. Bone c. Soft tissue d. Water

b. Bone, which has a propagation speed of 4080 m/s, has the highest propagation speed.

46. If only the density of a medium is increased, then the: a. Propagation speed will increase b. Propagation speed will decrease c. Propagation speed will stay the same d. None of the above

b. If only the density of the medium is increased, then the propagation speed will decrease.

37. What is the change in intensity if the power decreases by half? a. Intensity doubles b. Intensity is halved c. Intensity is one fourth d. Intensity does not change

b. If power is decreased by half, intensity is decreased by half.

19. If pulse repetition frequency increases, then the duty factor: a. Remains constant b. Increases c. Decreases d. Doubles

b. If the pulse repetition frequency increases, the duty factor increases.

41. What is pressure measured in? a. feet, inches, centimeters, or miles b. pascals or pounds per square inch c. kilograms per centimeter cubed d. hertz, kilohertz, or megahertz

b. Pressure is measured in pascals or pounds per square inch.

7. Pressure is typically expressed in: a. Frequency b. Pascals c. Decibels d. Kilograms per centimeter cubed

b. Pressure is typically expressed in pascals.

45. The portion of the sound beam where the molecules are pulled apart describes an area of: a. Compression b. Rarefaction c. Refraction d. Amplitude

b. Rarefaction is an area in the sound wave where the molecules are spread wider apart.

12. All of the following are true of stiffness except: a. It is defined as the ability of an object to resist compression b. Stiffness and propagation speed are indirectly associated c. Increasing stiffness increases propagation speed d. Stiffness may also be referred to as elasticity

b. Stiffness and propagation speed are directly related: the stiffer the medium, the faster the propagation speed.

30. If the angle of incidence is 40, what is the angle of transmission at the interface if medium 1 has a propagation speed of 1320 m/s and medium 2 has a propagation speed of 1700 m/s? a. 40 b. 40 c. 40 d. Cannot tell the angle of transmission

b. The angle of transmission is greater than 40.

35. The duty factor for continuous wave ultrasound is: a. 99% b. 100% c. 20,000 Hz d. 8 Pa

b. The duty factor for continuous wave ultrasound is 100%.

17. What is the total amount of attenuation that occurs if a 6.0-MHz sound beam travels through 4 cm of soft tissue? a. 24 dB b. 12 dB c. 6 dB d. None of the above

b. The total amount of attenuation that occurs if a 6.0-MHz sound beam travels through 4 cm of soft tissue is 12 dB.

8. The typical range of frequency for diagnostic ultrasound imaging is: a. 20 to 20,000 Hz b. 1 to 20 MHz c. 10 to 20 MHz d. 12 to 100 MHz

b. The typical range of frequency for diagnostic ultrasound is 1 to 20 MHz.

36. All of the following relate to the strength of the sound wave except: a. Amplitude b. Wavelength c. Intensity d. Power

b. Wavelength does not relate to the strength of the sound wave

23. All of the following are true of wavelength except: a. It is determined by both the medium and the sound source b. It is equal to the period divided by the frequency c. It is inversely related to frequency d. It is directly related to period

b. Wavelength is equal to the propagation speed divided by the frequency.

49. Which of the following would be considered ultrasonic? a. 10 Hz b. 12.5 Hz c. 1 MHz d. 200 Hz

c. 1 MHz is an ultrasonic frequency.

5. As imaging depth increases, the pulse repetition frequency must: a. Not change b. Increase c. Decrease d. Pulse repetition frequency does not relate to imaging depth

c. As imaging depth increases, the PRF decreases.

39. What is defined as the ability of the ultrasound system to image structures that are positioned parallel to the sound beam as separate structures? a. Transverse resolution b. Parallel resolution c. Axial resolution d. Coronal resolution

c. Axial resolution is the ability to resolve reflectors that lie parallel to the beam as distinct echoes.

42. What is essentially equal to the power of a wave divided by the area over which the power is distributed? a. Amplitude b. Power c. Intensity d. Absorption

c. Intensity is essentially equal to the power of a wave divided by the area over which the power is distributed.

25. Which of the following is defined as the number of ultrasound pulses emitted in 1 second? a. Pulse repetition period b. Duty factor c. Pulse repetition frequency d. Spatial pulse length

c. Pulse repetition frequency is defined as the number of ultrasound pulses emitted in 1 second.

31. The change in the direction of the original sound wave that occurs when sound interacts with two different tissue types that have a different propagation speed is referred to as: a. Wavelength b. Scattering c. Refraction d. Absorption

c. Refraction is the change in direction of the transmitted sound beam that occurs with oblique incidence and dissimilar propagation speeds.

14. Spatial pulse length can be calculated by: a. Multiplying the number of cycles times the frequency b. Dividing the period by the frequency c. Multiplying the number of cycles times the wavelength d. Dividing the number of cycles by the wavelength

c. Spatial pulse length equals the number of cycles in the pulse multiplied by the wavelength.

20. The percentage of time that the ultrasound system is producing pulses of ultrasound describes the: a. Pulse repetition period b. Pulse duration c. Duty factor d. Pulse repetition frequency

c. The duty factor is the percentage of time the ultrasound system is producing a sound.

27. The inertia of the medium describes its: a. Attenuation characteristics b. Stiffness c. Density d. Elasticity

c. The inertia of a medium describes its density.

43. Transducers have material within them that, when electronically stimulated, produces ultrasound waves. This is most likely some form of: a. Copperhirm titonize b. Zinconian sulfate c. Lead zirconate titanate d. Barium

c. Transducers have material within them that, when electronically stimulated, produces ultrasound waves. These materials most likely consist of some form of lead zirconate titanate.

48. The maximum value or minimum value of an acoustic variable minus the equilibrium value of that variable describes the: a. Power b. Intensity c. Duty factor d. Amplitude

d. Amplitude is the maximum or minimum deviation of an acoustic variable from the average value of that variable.

16. As a sound wave travels through the human body, the intensity of the sound wave decreases as a result of: a. Attenuation b. Absorption c. Scattering d. All of the above

d. Attenuation is a decrease in the amplitude, power, and intensity of the sound beam as sound travels through tissue. There are three mechanisms of attenuation: absorption, reflection, and scattering

44. What is the change in power if the amplitude triples? a. It doubles b. It triples c. It quadruples d. It increases nine times

d. If amplitude triples, then power increases by nine times.

34. In clinical imaging, the wavelength measures between: a. 1 and 10 Hz b. 1540 and 2000 m/s c. 0 and 1 d. 0.1 to 0.8 mm

d. In clinical imaging, the wavelengths measure between 0.1 and 0.8 mm.

4. Which of the following would have the lowest propagation speed? a. Water b. Soft tissue c. Bone d. Lung tissue

d. Lung tissue, which has a propagation speed 660 m/s, has the lowest propagation speed.

26. Which of the following is defined as only the active time? a. Duty factor b. Pulse repetition frequency c. Period d. Pulse duration

d. Pulse duration is only the active time or "on" time.

6. Which of the following describes the amount of refraction that occurs at an interface? a. Bernoulli's law b. Poiseuille's law c. Law of reflection d. Snell's law

d. Refraction is a redirection of the transmitted sound beam. Snell's law describes the angle of transmission at an interface based on the angle of incidence and the propagation speeds of the two media.

47. Sound is technically a: a. Transverse and longitudinal wave b. Mechanical and transverse wave c. Nonmechanical and pressure wave d. Mechanical and longitudinal wave

d. Sound is technically a mechanical and longitudinal wave.

50. Which of the following is considered the speed of sound in soft tissue? a. 660 m/s b. 330 m/s c. 1480 m/s d. 1540 m/s

d. The average speed of sound in all soft tissue is considered to be 1540 m/s or 1.54 mm/s.

24. Which of the following is determined by the sound source and medium? a. Propagation speed b. Frequency c. Period d. Wavelength

d. Wavelength is determined by both the sound source and the medium.

11. Which of the following is described as the distance over which one cycle occurs? a. Pulse duration b. Duty factor c. Period d. Wavelength

d. Wavelength is distance over which one cycle occurs, or the distance from the beginning of one cycle to the end of the same cycle.