Chapter 3 - UltrasoundPhysics

the propagation speed of continuous wave ultrasound is 1.8 kilometers per second. The wave is then pulsed with a duty factor of 50%. What is the new propagation speed? a. 0.5 km/sec b. 0.9 km/sec c. 1.8 km/sec d. 3.6 km/sec e. cannot be determined

c. 1.8 km/sec

what is the best estimate for the speed of sound in tendon? a. 1000 m/s b. 1540 m/s c. 1754 m/s d. 5,400 m/s

c. 1754 m/s

the wavelength of an ultrasonic wave is determined by: a. the sound source b. the medium through which the wave travels c. both a and b d. neither a nor b

c. both a and b

what determined the intensity of an ultrasound beam after it has traveled through the body a. the sound wave source b. the medium through which the sound travels c. both a and b d. neither a nor b

c. both a and b

Mathematically, when a number is squared, the number is multiplied by: a. 2 b. 0.5 c. itself d. 1.5

c. itself

which pulse has a lower propagation speed? a. the 10 MHz pulse b. the 2 MHz pulse c. neither pulse d. cannot be determined

c. neither pulse

what is the best estimate of the distance that sound can travel in soft tissue in one second? a. one yard b. one hundred yards c. one mile d. ten miles

c. one mile

the intensity of an ultrasound beam is defined as the ___ in a beam __ by the ___ of the beam. a. power multiplied, diameter b. amplitude, divided, area c. power, divided, area d. amplitude, multiplied, circumference

c. power, divided, area

the power of an ultrasound wave can be reported with which of the following units? a. watts/square centimeter b. dB/cm c. watts d. kg/cm^2

c. watts

Using a particular ultrasound system and transducer, can amplitude (initial) be changed by the operator?

can

Using a particular ultrasound system and transducer, can power be changed by the operator?

can

Using a particular ultrasound system and transducer, can frequency be changed by the operator?

can not

Using a particular ultrasound system and transducer, can period be changed by the operator?

can not

Using a particular ultrasound system and transducer, can propagation speed be changed by the operator?

can not

when the power in an acoustic beam is doubles and the cross-sectional area of the beam is halved, the intensity of the beam is: a. doubled b. halved c. quartered d. 4 times larger

d. 4 times larger

which pulse has the longest SPL? a. the 10 MHz wave b. the 2 MHz wave c. neither wave d. cannot be determined

d. cannot be determined

which pulse has the lowest power? a. the 10 MHz pulse b. the 2 MHz pulse c. neither pulse d. cannot be determined

d. cannot be determined

as a general rule which of the following lists media in increasing order of propagation speed? a. gas, solid, liquid b. liquid, solid, gas c. solid, liquid, gas d. gas, liquid, solid

d. gas, liquid, solid

a sonographer adjusts the output power of the wave admitted by the transducer. Which of the following also changes? a. PRP b. PRF c. propagation speed d. intensity

d. intensity

which of the following terms best describes the relationship between frequency and wavelength for sound traveling in soft tissue a. reciprocal b. direct c. related d. inverse

d. inverse

The final amplitude of an acoustic wave is reduced to one half of its original value. The final power is __ the original power. a. the same as b. one-half c. double d. none of the above

d. none of the above

How are amplitude and intensity related?

directly

How are amplitude and power related?

directly

How are power and intensity related?

directly

How are stiffness and sound speed related?

directly

T or F? The ultrasound wave travels much faster than the audible wave.

false

T or F? The wavelength of the 5 MHz wave is greater than the wavelength of the 5 kHz wave.

false

T or false? The power in the wave increases as it travels through the mass.

false

t or f? The frequency of the wave increases as it travels through the mass

false

Does the medium or the sound source determine propagation speed?

medium

What are the units of propogation speed?

meters/seconds

What are the units of wavelength?

millimeters (mm)

What are the units of period?

second

Does the medium or the sound source determine power? (initial)

sound source

T or F: with diagnostic imaging instruments, the operator can alter the intensity of an ultrasound beam produced by a transducer

true

T or F? the period of the 5 MHz wave is less than the period of the audible wave.

true

How are frequency and intensity related?

unrelated

How are frequency and sound speed related?

unrelated

How are power and frequency related?

unrelated

How are wavelength and intensity related?

unrelated

Which of the following are considered acoustic variables? (More than one may be correct) A. Frequency B. Density C. Particle motion D. Temperature E. Period F. Pressure

B, C, & F

A top is spinning on a table. What is the period of the spinning top? A. 4 pounds B. 8 doll hairs C. 0.05 seconds D. 3 cm

C. Of the available answers, the only one that has units of time is 0.05 seconds. This must be the answer.

If the power in a beam is 1 watt and the area is 5 cm2, what is the beam's intensity? A. 5 W/cm^2 B. 1 W/cm^2 C. 0.2 W/cm^2 D. 1 watt

C. To answer this question, concentrate on the units. Intensity has a units of W/cm^2. Thus, we must find out how many watts there are, and divide them by the number of cm^2. The question states there is only 1 watt. The area is 5 cm^2. Thus, the intensity is 1/5, or 0.2 W/cm^2.

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

False. In diagnostic imaging, the frequency of the sound wave generally remains constant and does not routinely change as the sound propagates through the body. Slight changes in frequency occur when sound strikes moving structures. This forms the basis for Doppler ultrasonography.

Which of the following are considered acoustic parameters? (more than one may be correct) A. Frequency B. Density C. Distance D. Pressure E. Period

A & E

Which of the following units are appropriate to describe the period of an acoustic wave? A. minutes B. microseconds C. meters D. mm/µs E. cubic centimeters

A and B. The period of a wave is defined as the time that elapses as a wave oscillates through a single cycle. The units for period must be a measure of time and such as minutes or seconds. A and B are the units of time. The incorrect selections C, D, and E are units of distance, speed and volume, respectively.

Identify all the waves that are inaudible. A. 4 MHz B. 400 kHz C. 28 Hz D. 2 Hz

A, B, D. These 3 waves are inaudible and cannot be hear by humans. Choices A and B are utrasonic, whereas D is infrasonic. Humans cannot hear infrasound or ultrasound.

Which of the following best describes the line identified by the letter C? A.Amplitude B. Peak-to-peak amplitude C. Frequency D. Wavelength E. N/A

A. Amplitude

Of the four waves whose frequencies are listed below, which has the shortest period? A. 12 kHz B. 6,000 Hz C. 205 Hz D. 1 kHz

A. Of the 4 choices, A has the highest frequency and, thus, the shortest period.

The characteristics of four media are described below. Which of the media has the slowest propagation speed? A. high density and high elasticity B. low density and high stiffness C. low stiffness and low density D. low compressibility and low stiffness

A. Speed is determined by density and stiffness of a medium (the opposite of stiffness is elasticity). When a medium has high elasticity, its speed is slow. A medium with a high density also has a slow speed. The medium described in choice A has the lowest propagation speed.

What determines the period of an ultrasound wave? A. the Transducer B. the medium through which the sound travels C. both A and B D. Neither choice A nor B

A. The sound source (transducer) that produces an acoustic signal determines the period of a wave. The wave's period is unrelated to the medium through which the sound travels, and will not change as the wave moves from one medium to another.

What establishes the frequency of an ultrasound wave? A. the transducer B. the medium through which the sound travels C. Both A and B D. Neither choice A nor B

A. When created by a transducer, an ultrasound wave has a specific frequency. The frequency is not determined by the medium through which the sound travels. Only the sound source (transducer) establishes the wave's frequency.

Propagation speed can be correctly recorded with which of the following units? More than one may be correct. a. miles per hour b. mm /sec c. km/sec d. inches per year

ALL are CORRECT

The effects of a medium on an ultrasound wave are called _______________.

Acoustic Propagation properties

The effects of tissue on sound waves are called ________________.

Acoustic Propagation properties

Which of the lines above, A, B, C, is most likely to be determined by the source and the medium?

B

The speed at which a wave travels through a medium is determined by _____: A. the sound wave's properties only B. the medium's properties only C. properties of both wave and medium D. none of the above

B, Speed is determined by the characteristics of the medium only. The characteristics of the wave do not affect its speed. All sound waves of any frequency, period, intensity, and power travel at the same speed in particular medium.

Of the four waves whose periods are listed below, which has the highest frequency? A. 8 s B. 80 µs C. 8 Ms D. 800 ks

B, The wave with a period of 80 µs has the highest frequency, Period and frequency have an inverse relationship. Thus, the wave with the shortest period has the highest frequency.

What is the range of periods commonly found in waves produced by ultrasound systems? A. 0.001 to 1s B. 0.06 to 0.5 µs C. 0.2 to 1 ms D. 10 to 100 ns

B, Ultrasonic imaging waves have a period in the range of 0.06 to 0.5 µs. The period is the time of a single cycle. Period is the reciprocal of frequency. A wave with a frequency of 2 MHz has a period of 0.5 µsec. A wave with a frequency of 15 MHz has a period of 0.06 µs.

Identify the wave that is ultrasonic. A. 400 mHz B. 4 MHz C. 28 Hz D. 2 Hz

B. A wave with a frequency greater than 20,000 Hz cannot be hear because its frequency is higher than the upper limit of hearing.

Which of these waves is ultrasonic and most useful in diagnostic sonography? A. 400 MHz B. 4 MHz C. 2 kHz D. 200,000 Hz

B. Although choices A, B, & D are all ultrasonic, only answer B falls within the typical range of frequencies used in diagnostic sonography.

What is the wavelength of 2 MHz sound in soft tissue? A. 1.54 mm B. 0.77 mm C. 0.51 mm D. 1.54 km/s E. 3.08 mm

B. In soft tissue, wavelength equals 1.54 mm divided by the frequency in MHz. Thus 2 MHz sound will have a wavelength of 0.77 mm.

Infrasound is defined as a sound with a frequency of _______. A. greater than 20,000 kHz B. less than 20 Hz C. greater than 10 MHz D. less than 0.02 MHz

B. Infrasound is defined as an acoustic wave with a frequency so low that it is not audible to humans. Infrasound is an inaudible wave with a frequency of less than 20 Hz.

If intensity remains the same while the power is doubled, what has happened to the beam area? A. Quadrupled B. Doubled C. Halved D. Unchanged

B. Recall that intensity equals power divided by area. If intensity remains unchanged, then whatever happens to power must also happen to area. In this vase, power has doubled. Therefore, area must have doubled as well.

If sound travels at exactly 1,540 m/sec in a particular medium, then the medium ________. A. must be soft tissue B. may be soft tissue C. cannot be soft tissue

B. Sound waves travel exactly 1540 m/sec in soft tissue. However, the media have the same propagation speed as that of soft tissue. The medium in question could be soft tissue, or it could be something else.

Which of the following characteristics will create the fastest speed of sound? A.High density, high stiffness B. Low density, high stiffness C. High density, low stiffness D. Low density, low stiffness

B. Speed is inversely

What is the speed of sound in air? A. 1,540 m/s B. 330 m/s C. 100 m/s D. 3,010 m/s

B. The speed of sound in air is 330 m/s, substantially lower than the speed of sound in soft tissue

The propagation speeds of ultrasound waves in muscle, liver, kidney, and blood are _____. A. exactly the same B. very similar to each other C. vastly different

B. The speed of sound in these media are less than 5% different from each other. The characteristics of muscle, kidney, liver, and blood that determine the wave's speed in the media are quite similar.

What term describes the number of cycles that an acoustic variable completes in a second? A. Period B. Frequency C. Pulse repetition period D. Variable rate

B. This is the definition of the term frequency. Frequency can also be thought of as the number of regularly occurring events in a specific time.

The effects of sound waves on tissue in the body are called _______________.

Bioeffects

Which of the following waves has the longest period? A. 2 MHz B. 4,000 Hz C. 6 Hz D. 1 kHz

C, The wave with a frequency of 6 Hz has the longest period. Period and frequency have an inverse relationship. Thus, the wave with the lowest frequency has the longest period.

Of the four waves whose periods are listed below, which has the lowest frequency? A. 8 s B. 80 µs C. 8 Ms D. 800 ks

C, The wave with the longest period has the lowest frequency. Choice C has a period of 8 million seconds (8 Ms), which is the longest period.

A sound beam travels a total of 10 cm in 2 seconds. What is the speed of sound? A. 10 cm/sec B. 2 cm/sec C. 5 cm/sec D. 0.2 cm/sec

C. 10 cm/2 sec = 5 cm/sec

When the elasticity of a medium is high, the ____ is high. A. stiffness B. Propagation speed C. compressibility D. reflectivity

C. Both elasticity and compressibility describe the ability of a medium to reduce its volume when affected by a force. High elasticity means the same as high compressibility.

With standard ultrasonic imaging, what happens to the period of a wave as it propagates? A. Increases B. Decreases C. Remains the same

C. Certain parameters of a wave change as the wave travels through the body. However, the period and the frequency of a wave typically remain constant as a sound wave propagates.

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. A is one-third as long as B B. A is the same as wave B C. A is three times as long as B D. cannot be determined

C. Frequency and period are reciprocals. If the frequency of one wave is one-third as large as another, then the period of the wave will be three times longer than the other.

_________ is the reciprocal of period. A. Inverse period B. pulse repetition period C. frequency D. propagation period

C. Frequency is the reciprocal of period. Reciprocals are related in two ways: 1) As one increases, the other decreases. 2) When they are multiplied together, the result is unity. For example, a wave with a period of one-hundredth of a second has frequency of 100 per second or 100 Hz.

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? A. 0.5 B. 0.5 MHz C. 5 MHz D. 10 MHz

C. Frequency is the reciprocal of the period. The fact that a wave is pulsed rather than continuous does not alter the frequency of the signal. The new and old frequencies are the same, 5 million/second.

When a sonographer increases the maximum imaging depth during tan exam, what happens to the frequency? A. Frequency increases B. Frequency decreases C. Remains unchanged

C. Imaging depth and frequency are unrelated. When the depth of view is increased, the frequency of sound remains the same.

What is the wavelength of 3 MHz sound in soft tissue? A. 0.51 m B. 0.51 km C. 0.51 mm D. 0.51 nm E. 0.51 µm

C. In soft tissue, wavelength equals 1.54 mm divided by the frequency in MHz. Thus, 3 MHz sound will have a wavelength of 0.51 mm.

Which of the following characteristics will create the slowest speed of sound? A.High density, high stiffness B. Low density, high stiffness C. High density, low stiffness D. Low density, low stiffness

C. Speed is inversely proportional to density and directly proportional to stiffness.

Compressibility describes a characteristics of a medium. Which two terms describe the same property as compressibility? A. density and stiffness B. density and conductance C. stiffness and elasticity D. elastance and impedance

C. The compressibility of a medium describes its ability to reduce its volume when a force is applied to it. For example, a marshmallow is compressible because when it is squeezed, it gets smaller. Elasticity has the same meaning as compressibility. Stiffness describes this same characteristic; however, stiffness is the opposite of compressibility.

Two sound waves with frequencies of 5 and 3 MHz travel to a depth of 8 cm in a medium and then reflect back to the surface of the body. Which acoustic wave arrives first at the body? A. the 5 MHz wave B. the 3 MHz wave C. neither D. cannot be determined

C. They both travel at the same speed and reach the surface of the body at exactly the same time. All sound waves, regardless of their features, travel at the same speed in a specific medium. The fact that these waves have different frequencies is irrelevant.

Using a particular ultrasound system and transducer, can intensity be changed by the operator?

Can

Using a particular ultrasound system and transducer, can the wavelength be changed by the operator?

Can not

Which of the lines above, A, B, C, or D, is most likely to the reciprocal of frequency?

D

Which of the following waves is infrasonic? A. 4 MHz B. 400 kHz C. 28 Hz D. 2 Hz

D. A wave with a frequency less than 20 Hz cannot be heard because its frequency is less than the lower limit of human hearing.

What is the range of frequencies emitted by transducers used in ultrasonic imaging? A.1 to 3 MHz B. 1 to 1,000 kHz C. -10,000 to +10,000 Hz D. 2,000,000 to 15,000,000 Hz

D. Frequencies commonly used in diagnostic imaging range from approximately 2 to 15 million cycles per second.

Which of the following best describes the line identified by the Letter D? A.Amplitude B. Peak-to-peak amplitude C. Frequency D. Period E. N/A

D. Period

What is the period of the earth's rotation around the sun? A. 1 day B. 1 hour C. 1 month D. 1 year

D. The earth completes one cycle around the sun in one year.

What two properties establish sound's propagation speed in a given medium? A. elasticity and stiffness B. stiffness and impedance C. conductance and density D. density and stiffness

D. The properties of the medium that affect sound's propagation speed are density and stiffness.

What is the propagation speed of a 5 MHz sound wave in soft tissue? A. 1,450 m/s B. 1,540 m/s C. 1.54 m/s D. 1.54 mm/µs

D. The speed of any sound wave moving through soft tissue, regardless of frequency, is 1.54 mm/µsec, 1,540 m/sec, or 1.54 km/sec.

Ultrasound is defined as a sound with a frequency of ______. A. greater than 20,000 kHz B. less than 1 kHZ C. greater than 10 MHz D. greater than 0.02 MHz

D. Ultrasound is defined as an acoustic wave with a frequency so high that it is not audible to humans. Ultrasound is an inaudible wave with a frequency of at least 20,000 Hz, 20 kHz, or 0.02 MHz.

Which of the following best describes the line identified by letter D? A.Amplitude B. Peak-to-peak amplitude C. Frequency D. Wavelength E. N/A

D. Wavelength

What is characteristic of acoustic waves with frequencies exceeding 20,000 Hz when compared with waves having frequencies of less than 20,000Hz? A. they travel more effectively in soft tissue B. they travel more rapidly C. they attenuate less when traveling soft tissue D. humans can't hear them

D. Waves with frequencies exceeding 20 kHz are inaudible to humans and are called ultrasonic. They ravel at the same speed as waves with lower frequencies and attenuate at a faster a rate than waves with lower frequencies.

What is characteristic of acoustic waves with frequencies of less than 20 Hz when compared with waves having frequencies of more than 20 Hz? A. they travel less effectively in soft tissue B. they travel more rapidly C. they attenuate more when traveling in soft tissue D. humans can't hear them

D. Waves with frequencies of less than 20 Hz are inaudible to humans and are called infrasonic. They travel at the same speed as waves with higher frequencies and attenuate at a lesser rate than waves at higher frequencies.

What is the wavelength of a wave with an unknown frequency traveling in soft tissue? A. 0.51 µm B. 0.51 m/s C. 0.51 pascals D. 0.51 watts E. 0.51 mm

E is the only answer with units of distance. Choice A has units of time, B has units of speed, C has units of pressure, and D has units of power. Therefore, the only possible choice is E.

Which of the following cannot be considered a unit of frequency? A. per day B. cycles/sec C. Hz D. hertz E. cycles

E, The term cycles inform us the number of events but does not inform us of the duration of time required for those events to occur. Choice E is incomplete and is not a unit of frequency. All the other choices reveal that a number of events took place in a specific time span.

Which of the following best describes the line identified by the letter B? A.Amplitude B. Peak-to-peak amplitude C. Frequency D. Wavelength E. N/A

E. N/A. None of the above. Line B is actually two wavelengths.

Which of the following best describes the line identified by the letter A? A: Amplitude B: Period C: Frequency D. Wavelength E. Peak-to-peak amplitude

E. Peak-to-peak amplitude

T or F? Lower frequency sound creates higher quality images with greater detail.

False

True or false? The wavelength of an acoustic wave is shorter when its pulsed rather than continuous

False

t or f? the period of the sound wave decreases as it travels through the mass.

False

True or False. If the amplitude of a wave is increased to 3 times its original value, the intensity is increased by 6 times.

False. Intensity is proportional to the amplitude squared. If we triple the amplitude, we increase the intensity by a factor of nine.

True or false. If the power of a wave is halved, the intensity is reduced to one-fourth its original value.

False. Intensity is the power of a beam divided by its cross-sectional area. If we halve the power, we will halve the intensity.

True or False. Propagation speed increases as frequency increases.

False. Propagation speed is determined by the medium only. Frequency and speed are unrelated.

True or False. Propagation speed increases as frequency decreases.

False. Speed and Frequency are unrelated.

True or False, Propogation Speed increases as frequency increases.

False. Speed and frequency are unrelated.

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

False. The sonographer cannot adjust the period (or frequency) of a wave produced by a basic transducer. Think of striking a key on a piano. The frequency of sound created by striking a single key is constant. If the sound beam's frequency and period are not suited for the particular type of imaging, the sonographer must select a new transducer with a different frequency.

What are the units of frequency?

Hertz (Hz)

How are acoustic velocity and compressibility related?

Inversely

How are acoustic velocity and density related?

Inversely

How are elasticity and speed of sound related?

Inversely

How are frequency and period related?

Inversely

How are wavelength and frequency related?

Inversely

Medium 1 has a density of 9 and a stiffness of 6. Medium 2 has a density of 8 and a stiffness of 6. In which medium will sound travel slower?

Medium 1. Since both media have the same stiffness, the medium with the greater density has the lower propagation speed.

Does the medium or the sound source determine amplitude? (initial)

Sound source

Does the medium or the sound source determine frequency?

Sound source

Does the medium or the sound source determine intensity? (initial).

Sound source

Does the medium or the sound source determine period?

Sound source

Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5 mW and 15 mW. They all travel through three media -wood, brick, and fat - with identical thicknesses of 5 cm. Are the following 3 statements true or false?

The sound waves travel through all three media at different speeds because the waves have different powers. False

Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5 mW and 15 mW. They all travel through three media -wood, brick, and fat - with identical thicknesses of 5 cm. Are the following 3 statements true or false?

The waves travel through all three media at different speeds because the media are different. True

Three sound waves with identical frequencies of 3 MHz have powers of 2 mW, 5 mW and 15 mW. They all travel through three media -wood, brick, and fat - with identical thicknesses of 5 cm. Are the following 3 statements true or false?

The waves travel through all three media at the same speed since they have identical frequencies. False

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

True

T or F? The wavelength increases while the wave travels through the mass.

True

T or F? a sonographer can routinely change the power of a wave emitted by a transducer used in diagnostic ultrasonic imaging. True

True

true or false? Shorter wavelength sound creates higher quality images with greater details

True

t or F? Both the 5 MHz and the 5 kHz waves travel at similar speeds through the medium.

True All sound waves travel at exactly the same speed while moving through a particular medium

True or False? Soft tissue is an imaginary construct that actually does not exist.

True, soft tissue is an imaginary structure with characteristics that represent an "average" of body tissues, including muscle, blood, kidney, and spleen. It is used as an approximation.

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

True. Frequency and period are reciprocals. When the periods of two waves are identical, the frequencies of the waves must also be identical.

True or False. Propagation Speed does not change as frequency increases.

True. Propagation speed and frequency are unrelated.

True or 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. The period of a wave is a characteristic of each individual cycle in the wave. The period of a wave (as well as frequency and wavelength) remains unchanged, whether the wave is continuous or pulsed.

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

True. The primary difference between audible and ultrasonic waves is that humans can hear audible waves. A wave's behavior or adherence to physical laws and principles is generally the same regardless of whether it can be hear by humans.

True or false. A wave with a frequency of 15,000 MHz is ultrasonic?

True. Ultrasound is defined as any wave with a frequency greater than 20,000 hertz. 15,000 MHz is a frequency of 15,000,000,000 Hz!

What are the units of power?

Watts

What are the units of intenisty?

Watts/cm^2

what is the wavelength of 2 MHz sound in soft tissue? a. 0.77 mm b. cannot be determined c. 1.54 mm d. 2 mm

a. 0.77 mm

the maximum value of the density of an acoustic wave is 60 Ib/in ^2 while the minimum density is 20 Ib/in^2 what is the amplitude of the wave? a. 20 Ib./in^2 b. 40 lb./in^2 c. 60 Ib./in^2 d. none of the above

a. 20 Ib./in^2

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 waves final power. a. 3 watts b. 9 watts c. 1 watt d. none of the above

a. 3 watts

which of the following are acceptable units for the amplitude of an acoustic wave? More than one answer a. cm b. pascals c. gauss d. watts

a. cm b. pascals

As an ultrasound wave travels through the body its amplitude usually a. decreases b. increases c. stays the same d. cannot determine

a. decreases

typically, as an ultrasound wave travels through soft tissue, the power of the wave: a. decreases b. increases c. remains the same

a. decreases

The speed of sound traveling through bone is ___ soft tissue a. higher than b. lower than c. equal to d. cannot be determined

a. higher than

what happens to an acoustic beams intensity when the power and the beam increases by 25% while the cross- sectional area of the beam remains the same? a. increases by 25% b. increases by 75% c. increases by 50% d. increases by 25%

a. increases by 25%

What determines the initial intensity of an ultrasound beam a. the sound of the sound wave b. the medium through which sound travels c. both a and b d. neither a nor b

a. the sound of the sound wave

What determines the initial amplitude of an ultrasound wave? a. the transducer b. the medium in which sound travels c. both a and b d. neither a or b

a. the transducer

if the power of the beam is tripled, while the cross-sectional area of the beam remains the same, the intensity __ a. triples b. increase nine-fold c. remains the same d. none of the above

a. triples

what are the units of the transmitted intensity of the sound wave a. w/cm^2 b. watts c. dB none, it is unit less

a. w/cm^2

What is the wavelength of 10 MHz sound in soft tissue? a. 0.77 mm b. 0.15 c. 1.54 mm d. 10 mm

b. 0.15 wavelength (mm) = 1.54/frequency (MHz)

as the sound travels in a body, what typically happens to the intensity of the wave a. increases b. decreases c. remains the same

b. decreases

the amplitude of an acoustic wave is increased, which of the following will most likely remain unchanged? a. power b. frequency c. period d. intensity

b. frequency c. period

what happens to the intensity of an ultrasound beam when the beams cross-sectional area remains unchanged while the amplitude of the wave triples? a. triples b. increases nine-fold c. remains the same d. none of the above

b. increases nine-fold

what happens when the power in an ultrasound beam is unchanged and at the same time the beam area doubles a. doubles b. is halved c. is quartered d. remained the same

b. is halved

compared to soft tissue the speed of an acoustic wave through lung tissue is ___ a. faster b. slower c. equal d. cannot be determined

b. slower

which pulse has a longer wavelength? a. the 10 MHz pulse b. the 2 MHz pulse c. neither pulse d. cannot be determined

b. the 2 MHz pulse

which sound wave has a longer period? a. the 10 MHz pulse b. the 2 MHz pulse c. neither pulse d. cannot be determined

b. the 2 MHz pulse

the wavelength of a cycle in an ultrasound wave can be reported with which units? a. units of time b. units of distance c. units of area d. mm only

b. units of distance

what are the units of intensity? a. watts b. watts/cm c. watts/cm^2 d. dB

b. watts/cm

Does the medium or the sound source determine wavelength?

both