Ultrasound Physics CH 2 Questions

Which of the following are acceptable units for the amplitude of an acoustic wave?

cm and watts

A pair of waves are in phase. What occurs when these waves interfere?

constructive interference

Which of the following cannot be considered a unit of frequency?

cycles

Sound can be characterized as:

cyclical oscillations in certain variables

As an ultrasound wave travels through the body, its amplitude usually:

decreases

As sound travels in the body, what typically happens to the intensity of the wave?

decreases

Typically, as an ultrasound wave travels through soft tissue, the power of the wave:

decreases

Two waves arrive at the same location and interfere. The resultant sound wave is smaller than either of the two original waves. What is this called?

destructive interference

When the power in an acoustic beam is doubled and the cross-sectional area of the beam is halved, then the intensity of the beam is:

four times larger

What term describes the number of cycles that an acoustic variable completes in a second?

frequency

______ is the reciprocal of period.

frequency

The amplitude of an acoustic wave is increased. Which of the following will most likely remain unchanged?

frequency, and period

Ultrasound is defined as a sound with a frequency of ____.

greater than 0.02 MHz

A particle within a transverse wave is traveling vertically. What is the direction of the waves propagation?

horizontal

What is characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000 Hz?

humans can't hear them

What is characteristic of acoustic waves with frequencies of less than 20 Hz when compared with waves having frequencies of more than 20 Hz?

humans can't hear them

What happens to the intensity of an ultrasound beam when the beam's cross-sectional area remains unchanged while the amplitude of the wave triples?

increases ninefold

A sonographer adjusts the output power of the wave emitted by the transducer. Which of the following also changes?

intensity

Waves that exist at the same location and time will combine. What is this called?

interference

What happens to an acoustic beam's intensity when the power in the beam increases by 25% while the cross-sectional area of the beam remains the same?

it increases by 25%

Mathematically, when a number is squared, the number is multiplied by:

itself

Which of the following types of waves do not require a medium in order to propagate? (More than one may be correct)

light, heat, television

Which of the following describes the characteristics of a sound wave?

mechanical, longitudinal

Which of the following units are appropriate to describe the period of an acoustic wave?

minutes and microseconds

The final amplitude of an acoustic wave is reduced to one-half of its original value. The final power is _____ the original power.

none of the above.

The intensity of an ultrasound beam is defined as the ____ in a beam _____ by the _____ of the beam.

power, divided, area

With standard ultrasound imaging, what happens to the period of a wave as it propagates?

remains the same

When a sonographer increases the maximum imaging depth during an exam, what happens to the frequency?

remains unchanged

What determines the intensity of an ultrasound beam after it has traveled through the body?

the sound wave's source and the medium through which the sound travels

What determines the initial intensity of an ultrasound beam?

the source of the sound wave

What determines the initial amplitude of an ultrasound wave?

the transducer

What determines the period of an ultrasound wave?

the transducer

What establishes the frequency of an ultrasound wave?

the transducer

All of the following are true about sound waves except _____.

they are transverse

The direction of motion of a particle in a wave is perpendicular to the direction of propagation of the wave. What type of wave is this?

transverse

If the power of the beam is tripled while the cross-sectional area of the beam remains the same, the intensity _____.

triples

A force is applied to a surface. If the force is tripled and the surface area over which the force is applied is also tripled, what is the new pressure?

unchanged

The power of an ultrasound wave can be reported with which of the following units?

watts

What are the units of intensity?

watts/cm2

Compare two sound waves, A and B. The frequency of wave A is one-third that of wave B. How does the period of wave A compare with the period of wave B?

A is three times as long as B

True or False? The sonographer has the ability to alter the period of an ultrasound wave that is produced by a basic transducer.

False

What happens when the power in an ultrasound beam is unchanged, and at the same time, beam area doubles?

is halved

Infrasound is defined as a sound with a frequency of _____.

less than 20 Hz

What is the range of periods commonly found in waves produced by ultrasound systems?

0.06 to 0.5 microseconds

Is frequency an acoustic variable? 1

1 False

Is pressure an acoustic variable? 2

2 True

What is the range of frequencies emitted by transducers used in ultrasonic imaging?

2,000,000 to 15,000,000 Hz

The maximum value of the density of an acoustic wave is 60 lb/in2 while the minimum density is 20 lb/in2. What is the amplitude of the wave?

20 lb/in2

Is propagation speed an acoustic variable? 3

3 False

The amplitude of an acoustic wave decreases from 27 pascals to 9 pascals. If the initial power in the wave was 27 watts, what is the wave's final power?

3 watts

Is wavelength an acoustic variable? 4

4 False

Is voltage an acoustic variable? 5

5 False

The frequency of a continuous acoustic wave is 5 MHz. The wave is then pulsed with a duty factor of 0.1. What is the new frequency?

5 MHz

Is intensity an acoustic variable? 6

6 False

Is Motion of particles in the wave an acoustic variable? 7

7 True

Is density an acoustic variable? 8

8 True

True or False?With standard ultrasound pulses, the frequency of the ultrasound changes significantly as the wave propagates through the body.

False

Correct units for particle motion?

Miles or centimeters

Correct units for pressure?

Pascals (Pa) or pounds per square inch (lb/in^2)

Correct units for density?

Pounds per inch cubed (lb/in^3) or kilograms per meters cubed (kg/m^3)

A sonographer can routinely change the power of a wave emitted by a transducer used in diagnostic ultrasonic imaging.

True

True of False?The period of an ultrasound wave is related to the frequency and is the same, regardless of whether the wave is pulsed or continuous.

True

True or False?If the periods of two waves are the same, then the frequencies of the waves must also be the same.

True

True or False?Waves in the ultrasound range behave in the same general manner as sound waves that are audible.

True

True or False?With diagnostic ultrasonic imaging instruments, the operator can alter the intensity of an ultrasound beam produced by a transducer.

True

True or False?With standard diagnostic imaging instrumentation, the sonographer has the ability to vary the amplitude of a sound wave produced by the transducer.

True

What are the units of the transmitted intensity of a sound wave?

W/cm2

Sound is best described as _____.

a series of compressions and rarefactions

As sound travels through a medium, what term describes the effects of the medium on the sound wave?

acoustic propagation properties

Which of the following is true of all waves?

all carry energy from one site to another

What are the units of a pressure measurement of an acoustic wave?

atmospheres (atm), pascals (Pa), millimeters of mercury (mm Hg), pounds/sq. inch (lb/in2)

What term is used to describe the effects of an ultrasound wave on living tissue?

biological effects