Physics Exam 1 Review Questions

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 substantially lower than the 330 m/s. speed of sound in soft tissue.

All of the following are true of sound waves except. A. they are acoustic B. they are pressure waves C. they are transverse D. they move energy

C. Sound waves are longitudinal, not transverse.

Which term is the reciprocal of mega? A. nano B. kilo C. macro D. micro

D. Mega means million. The reciprocal of million is millionth. Micro means millionth.

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.

True or False. A wave with a frequency of 15,000 MHz is ultrasonic. 5. 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.

List these metric terms in decreasing order: A. nano B. centi C. giga D. kilo E. hecto F. micro

The correct sequence of decreasing order is as follows: C, D, E, B, F, A, or giga, kilo, hecto, centi, micro, nano.

List these metric terms in increasing order: A. mega B. micro C. milli D. hecto E. deca F. deci

The correct sequence of increasin order is as follows: B, C, F, E, D, A. or micro, milli, deci, deca, hecto, mega.

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

True. A sonographer can alter the power of an ultrasound wave by adjusting a control on the ultrasound system. Power and amplitude are related; if the amplitude is increased, then so is the power. When the amplitude decreases, the power also decreases.

The maximum value of the density of an acoustic wave is 60 Ib/in? while the minimum density is 20 Ib/in2. What is the amplitude of the wave? A. 20 lb/in? B. 40 lb/in? C. 60 Ib/in? D. none of the above

A To calculate the amplitude subtract the minimum variable from its that number in half. In this maximum of a wave value of the acoustic and then divide case, the minus the minimum is 60- 20 maximum 40 lb/in?. Half of 40 is 20 Ib/in

Which of the following units are appropriate to describe the period of an acoustic wave? (More than one answer may be correct.) A. minutes B. microseconds C. meters D. mm/us E. cubic centimeters

A and B. The period of a waye 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, such as minutes or seconds. A and B are units of time. The incorrect selections C. D. and E are units of distance, speed, and volume, respectively.

What are the units of a pressure measurement of an acoustic wave? (More than one answer may be correct.) A. atmospheres (atm) B. pascals (Pa) C. millimeters of mercury (mm Hg) D. pounds sq. inch (Ibin?)

A, B, C, and D. All of these terms are appropriate to represent pressure (just as weight can be reported with units of pounds, ounces, tons, or grams). However, the pressure of sound waves is most often reported in units of pascals.

Propagation speed can be correctly recorded with which of the following units? (More than one may be correct.) A. miles per hour B. mm/msec C. km/sec D. inches per year

A, B, C, and D. Speed is recorded as a distance per unit of time, such as miles per hour, or feet/sec. Any relationship of distance per time is an acceptable answer.

Identify all the waves that are inaudible. (More than 1 answer may be correct.) A. 4 MHz B. 400 kHz C. 28 Hz D. 2 Hz

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

Which of the following types of waves do not require a medium in order to propagate? (More than one answer may be correct.) A. light B. heat C. sound D. television

A, B, and D. Sound cannot travel through a vacuum; it requires a medium in order to propagate. Other waveforms such as light, heat and TV waves are capable of traveling through a vacuum.

Which of the following are considered acoustic parameters? (More than one answer may be correct.) A. frequency B. density C. distance D. pressure E. period

A, E.

How many hertz is 3 MHz? A. 3,000,000 B. 3000 C. 333 D. 0.003

A. 3,000,000.

How much smaller is a hundred than a thousand? A. 1/10 B. 1/100 times C. 1/1000 times D. 1/10000 times

A. A hundred is one-tenth of a thousand.

The amplitude of an acoustic wave the initial decreases from 27 pascals to 9 pascals. If power in the wave was 27 watts, what is the wave's final power? A. 3 watts B. 9 watts C. 1 watt D. none of the above

A. Alterations in a wave's power are proportional to changes in its amplitude squared. The power is reduced to one-third of its previous value (from 27 to 9 pascals). One-third squared equals one-ninth. Thus, only one-ninth of the wave's original power remains. The initial power in the wave was 27 watts, one-ninth of that is 27/9, or 3 watts.

As an ultrasound wave travels through the body, its amplitude usually: A. decreases B. increases C. remains the same D. cannot be determined

A. As a sound wave travels in the body, its strength or amplitude diminishes. This process is called attenuation. We experience attenuation when walking away from a person who is speaking The further away we are from a speaker, the weaker that person's voice becomes.

Typically, as an ultrasound wave travels through soft tissue, the power of the wave: A. decreases B. increases C. remains the same

A. As a sound wave travels through the body, its power diminishes. This process is called attenuation. Amplitude and power are both measures of the strength of an acoustic wave, and tend decrease as sound travels.

What are the units of the transmitted intensity of a sound wave? A. W/cm2 B. watts C. dB D. none; it is unitless

A. As sound propagates, one of the ways to measure its strength is to record its intensity. The intensity of the part of a beam that continues to propagate in the forward direction as it reaches a boundary is called the transmitted intensity. It is reported in units w/cm2.

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.

All of the following are acoustic parameters except. A. pressure B. period C. propagation speed D. frequency

A. Pressure is an acoustic variable, not a parameter.

Sound is best described as A. a series of rarefactions compressions and wave B. a transverse C. a wave that humans D. an oblique acoustic energy can hear displacement of

A. Sound is composed of a series or compressions and rarefactions. Molecules in the medium are alternately squeezed together (compressed) and stretched apart (rarefied).

Which of the following best describes sound waves? A. a series of compressions and rarefactions B. waves that are heard by man C. movement of molecules and energy from one location to another D. waves that are used to make images of anatomy

A. Sound waves are series of compressions and rarefactions.

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 are the units associated with the circumference of a circle? A. mm B. mm? C. cm3 D. m4

A. The circumference of a circle is the length of the circle's outer boundary and is measured in units of length. B and C are units of area and volume. D has units of length to the fourth power, which has no meaning in geometry.

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? A. it increases by 25% B. increases by 75% C. it increases by 50% D. decreases by 25%

A. The intensity is equal to the power divided by the beam area. If the power increases 25% while the beam's area is unchanged, then the intensity is also increased by 25%.

A particle within a transverse wave is traveling vertically. What is the direction of the wave's propagation? A. horizontal B. vertical C. diagonal; both horizontal and vertical D. cannot be determined

A. The particles within a transverse wave travel in a direction that is perpendicular to the direction of propagation of the wave. If a transverse wave is traveling vertically, the particles in the wave are traveling horizontally. A water wave is a primarily a transverse wave. The wave propagates sideways along the surface of the water, while a ball floating on top of the water moves up and down as the wave passes.

The speed of sound traveling through bone is soft tissue. A. higher than B. lower than C. equal to D. cannot be determined

A. The propagation speed of sound in bone is higher than in soft tissue. Sound travels at a speed of 3 to 5 km/sec in bone. This is two to three times faster than soft tissue

What determines the initial intensity of an ultrasound beam? A. the source of the sound wave B. the medium through which the sound travels C. both A and B D. neither A nor B

A. The source of the acoustic wave determines the initial intensity (as well as the wave's amplitude and power). At its point of origin, the strength of an acoustic wave will not be related to the medium that the sound is about to enter.

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. The wavelength of sound in soft tissue is defined by the following relationship: wavelength (mm) = 1.54/ frequency (MHz) For 2 MHz sound, the wavelength is 1.54/2 or 0.77 MHz.

How is weight related to a sonographer's time spent exercising? A. inversely B. conversely C. directly D. unrelated

A. Two variables one variable are related when changes in result in changes in the other. When the changes follow in the opposite direction (one increases as the other decreases), the variables are inversely related.

What establishes the frequency of an ultrasound wave? A. the transducer B. the medium through which the sound travels C. both A and 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 (the transducer) establishes the wave's frequency.

If the power of the beam is tripled while the cross-sectional area of the beam remains the same, the intensity A. triples B. increases ninefold C. remains the same D. none of the above

A. When the cross-sectional area of a heam remains unchanged, the change in the intensity of a beam is proportional to the change in the power. The question states that the power is tripled. If the power is tripled, then the intensity is also tripled.

How is the age of a loaf of bread related to its freshness? A. inversely B. directly C. unrelated

A. inversely. As a loaf of bread ages, its freshness decreases.

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.

The amplitude of an acoustic wave is increased. Which of the following will most likely remain unchanged? (More than one answer may be correct.) A. power B. frequency C. period D. intensity

B and C. Amplitude relates to the strength of a wave. The frequency of a wave describes the number of cycles in one second. A wave's period is the time an acoustic variable oscillates though one complete cycle. Frequency and period are not related to amplitude, and remain unaltered when the amplitude changes.

Which of the following are considered acoustic variables? (More than one answer may be correct.) A. frequency B. density C. particle motion D. temperature E. period F. pressure

B, C, F.

How many milliliters are contained in a jar filled with 5 liters of fluid? A. 5 B. 5000 C. 500 D. 0.005

B. 5000.

How much bigger is one billion than one thousand? A. 1,000 times B. 1,000,000 times C. 10 times D. 10,000 times

B. A billion is one million times larger than a thousand. A million is 1,000,000.

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? A. it triples B. increases ninefold C. remains the same D. none of the above

B. A change in the intensity of a wave is proportional to the of the wave squared. change in the amplitude When the amplitude of a wave is tripled, the intensity is increased ninefold (3 x 3 = 9).

What is the reciprocal of 1/10? A. one-hundredth B. 10 C. 1/10 D. one-millionth

B. A pair of reciprocal numbers, when multiplied together, have a value of 1. In this case, 10 x 1/10 = 1.

How much bigger is a thousand than ten? A. 10 times B. 100 times C. 1000 times D. 500 times

B. A thousand is 100 times bigger than ten.

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 heard because its frequency is higher than the upper limit of human hearing.

As sound travels through a of the medium medium, what on the sound wave? term describes the effects A. toxic effects propagation properties B. acoustic C. bioeffects D. transmission properties

B. Acoustic propagation the effects of the medium properties describes on the wave traveling through it. Acoustic means "sound." Propagation means "to travel

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, and 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 (see page 34). Thus, 2 MHz sound will have a wavelength of 0.77 mm.

Infrasound is defined as a sound with 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.

How many nanoseconds are in 7 seconds? A. 7,000,000 B. 7,000,000,000 C. 7 million D. 0.00000007

B. Nano means billionth, There are one bililio billionths in one second. Therefore, there are seven billion billionths in seven seconds.

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 case, power has doubled. Therefore, area must have doubled as well.

All of the following are true about sound waves except A. they are mechanical B. they are transverse C. they carry energy from place to place D. they generally travel in a straight line

B. Sound waves are not transverse, they are longitudinal.

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 a particular medium.

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 proportional to density and directly proportional to stiffness.

As sound travels in the body, what typically happens to the intensity of the wave? A. increases B. decreases C. remains the same

B. The intensity of a sound beam decreases beam. They all decrease measure the strength of an ultrasound intensity are three different ways to attenuation. Amplitude, power, and as it travels through the body because of as sound propagates.

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. The speed of sound in lung tissue is slower than in soft tissue. Sound travels at speeds in the range of 0.5 to 1.0 km/sec in lung tissue.

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

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

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

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

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.

What is the range of periods commonly found in waves produced by ultrasound systems? A. 0.001 to 1 s B. 0.06 to 0.5 ps 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 us. 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 usec. A wave with a frequency of 15 MHz has a period of 0.06 us.

The wavelength wave can be reported of a cycle in an ultrasound with which units? A units of time (sec, min, etc.) B. units of distance (feet, etc.) C. units of area (m2, etc.) D. mm only

B. Wavelength is the distance from the end of one cycle. It has In soft tissue, and with beginning to the units of distance. frequencies typical of diagnostic wavelengths range from Although it may be impractical to record 0.15 to imaging, 0.75 mm. wavelengths in miles or meters, it can be done since they are distances.

Variations in all of the following identify specific waves as acoustic waves except: A. pressure B. parameters C. density D. acoustic variables

B. parameters

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

Bioeffects.

Sound can be characterized as: A, energy flowing through a vacuum B. a variable C. cyclical oscillations in certain variables D. a principle of acoustics

C. Sound is a wave. A wave is the rhythmical variation throughout time.

A sonographer measures the perimeter of an anatomical structure. Which of the following choices is a reasonable value for the measurement? A. 6 cm? B. 5 cc C. 15 mm D. 18 dB

C. "Perimeter" means the length of the outer boundary of a structure. For example, a square with an edge that is 5 inches long will have a perimeter measuring 20 inches (four sides, each with a length of 5 inches). Units of measurement in A, B, and D are not applicable to length.

A sound beam travels a total of 10 cm in 2 seconds. What is the speed of the 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.

How many kilometers are in 3000 meters? A. 1/300 B. 1/3 C. 3 D. 300 E. 3000

C. 3. Kilo means thousand. Three kilometers equal 3,000 meters.

How much bigger is a billion than million? A. 10 times B. 100 times C. 1000 times D. 500 times

C. A billion is 1000 times greater than a million.

What is the reciprocal of 1,000? A. one-hundredth B. 1,000 C. 0.001 D. one-millionth

C. A pair of reciprocal numbers, when multiplied together, have a value of 1. In this case, 1,000 x 0.001 = 1.

What is the reciprocal of 5? A. one-hundredth B. 5 C. 1/5 D. one-millionth

C. A pair of reciprocal numbers, when multiplied together, have a value of 1. In this case, 5 x 1/5 = 1.

Which types of waves will exhibit both constructive and destructive interference? A. waves of different amplitude B. a pair of longitudinal waves C. waves of different frequency D. out-of-phase waves

C. Both constructive and destructive interference occurs with waves with different frequencies.

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.

Select the sequence that appears in increasing order. A. mega, kilo, hecto, milli, giga B. nano, milli, micro, deci, deca, mega C. centi, deci, deca, hecto D. milli, hecto, centi, deci, nano, giga

C. Centi means "one-hundredth", deci means "one-tenth", deca means "ten", and hecto means "hundred." Thus, this sequence is increasing, starting from the smallest and ending with the largest.

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.

Which of the following is not a measure of area? A. square cm B. meters squared C. cubic meters D. feet x feet

C. Cubic meters are not used to measure area; they are used to measure volume. An area is measured in units of distance squared. For example, a rectangle's area is its length multiplied by its width, and can be reported in square feet, in, or square miles.

What is the best estimate for the speed of sound in tendon? A. 1,000 m/s B. 1,540 m/s C. 1,754 m/s D. 5,400 m/s

C. Sound travels slightly faster in tendon than in soft tissue.

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: • As one increases, the other decreases. • When they are multiplied together, the result is unity. For example, a wave with a period of one- hundredth of a second has a frequency of 100 per second or 100 Hz.

When a sonographer increases the maximum imaging depth during an 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 um

C. In soft tissue, wavelength equals 1.54 mm divided by the frequency in MHz (see page 34). Thus, 3 MHz sound will have a wavelength of 0.51 mm.

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

C. Of the abailable answers the only one that has units of time is 0.05 seconds.

What units are used to report the pressure of a sound beam? A. pounds B. centimeters C. pascals D. kg/cm

C. Pressure is appropriately reported with units of pascals, abbreviated Pa.

131. If sound doesn't travel at 1,540 m/sec in a medium, then the medium A. must be soft tissue B. may be soft tissue C. cannot be soft tissue

C. Sound waves travel exactly 1,540 m/sec in the medium cannot be soft tissue. sound in this medium is not 1,540 m/sec, soft tissue. Since t propagation speed of

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.

Waves that exist at the same location and time will combine. What is this called? A. inference B. rarefaction C. interference D. longitudinal interaction

C. The combination of many waves into a single wave is called interference.

Compressibility describes a characteristic 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.

What term is used to describe the effects of an ultrasound wave on living tissues? A. toxic effects B. acoustic propagation properties C. biological effects D. transmission properties

C. The effects of ultrasound on the tissues are called biological effects or bioeffects. There have been no confirmed bioeffects on humans with acoustic intensities typical of those used in diagnostic imaging.

What are the units of intensity? A. watts B. watts/cm C. watts/cm2 D. dB

C. The intensity beam divided by its cross-sectional area. of a beam is the power in the beam area has units of square cm. Power has units of watts and Intensity has units of watts/cm2.

The intensity of an ultrasound beam 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. The intensity of an ultrasound beam is the concentration of the power within the beam area. It is calculated by dividing the power in a beam by its area. The units of intensity are watts per centimeter squared, w/cm2

What determines the intensity of an ultrasound beam after it has traveled through the body? A. the sound wave's source B. the medium through which the sound travels C. both A and B D. neither A nor B

C. The source and the medium both ultimately determine the residual intensity of an ultrasound beam after it passes through the body. Sound waves attenuate as they propagate. The initial intensity of a sound beam is established by the source of the sound, the transducer. The frequency, which is also determined by the transducer, affects the rate of attenuation. In addition, the characteristics of the medium help to determine attenuation. For example, bone and lung have a greater attenuation rate than soft tissue. In contrast, water has a lower attenuation rate than soft tissue.

How are scores on the ultrasound board exams related to study time? A. inversely B. conversely C. directly D. unrelated

C. Two variables are related when changes in one variable result in changes in the other. When the changes go in the same direction (both increase or both decrease), the variables are directly related. Since scores increase as study time increases, these variables are directly related.

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. The speed of sound in a medium is determined only by the medium. There is no difference in sound's speed whether the new and old speeds will be identical, wave is continuous or pulsed. Thus, the 1.8 km/sec.

A bouquet has 30 flowers. The size of the bouquet is decreased by a factor of 3. How many flowers remain? A. 27 B. 0 C. 10 D. 15

C. The term "decrease by a factor" means to divide. 30/3 = 10.

The power of an ultrasound wave can be reported with which of the following units? (More than one answer may be correct.) A. watts/square centimeter B. dB/cm C. watts D. kg/cm?

C. The units of power are watts. This is the same measure of power as for light bulbs stereo systems, and curling irons.

How can the volume of an irregularly shaped object be measured most accurately? A. by visual inspection B. by its weight C. by immersing it in water D. by ultrasound scanning

C. The volume of any object can be accurately measured by immersing it in water and measuring the volume of water that is displaced.

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 ps 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.

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 surface body? A the 5 MHz wave B. the 3 MHz wave C. neither D. cannot be determined

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

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

C. To answer this question, concentrate on the units. Intensity has units of Wcm?. Thus, we must find out how many watts there are, and divide them by the number of cm2. The question states that there is 1 watt. The area is 5 cm?. Thus, the intensity is 15, or 0.2 cm2.

The speed of red blood cells traveling through a blood vessel is 750 cm/sec. You are asked to measure this speed in miles per hour. What information would be sufficient for you to complete your task? A. how many seconds in a minute and how many blood cells in the vessel B. the number of miles in a meter C. how many seconds per hour and the number of miles in a centimeter D. the direction of red blood cell motion and the Doppler shift frequency

C. To convert one unit to another requires a factor that relates the two terms, For how many length from example, to change a measurement of feet into inches, we must know inches are in a foot. In this case we are asked to convert cm per sec into miles per hour. Therefore, we require two pieces of information: the relationship between seconds and hours (relating one unit of time to another) and the relationship between miles and centimeters (relating one unit of distance to another). When units are changed, the actual amount does not change. For example, ten dimes provide the same purchasing power as four quarters. The units may be different, but the "total picture" remains the same.

Mathematically, when a number squared, the number is multiplied by: A. 2 B. 0.5 C. itself D. 1.5

C. To square a number means to multiply trhe number by itself. Hence, the term "five squared" means 5 times 5, or 25. Ten squared is 10 times 10, or 100.

The wavelength of an ultrasonic wavę 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. Wavelength is determined by both the sound source and the medium through which it travels. Wavelength is determined, in part, by the wave's frequency (which is established by the sound source). Wavelength is also affected by the speed of the sound wave, which is established by the medium. In a particular medium, higher frequency waves have shorter wavelengths. With a particular frequency, faster propagation speeds create longer wavelengths.

What do waves transfer from one location to another? A. matter B. molecules C. energy D. water

C. Waves carry energy from place to place.

Which of the following is not an appropriate unit for volume? A. cubic miles B. gallons C. cm D. cm3 E. pint

C. cm. Volume is measured in units of length cubed. Centimeters is simply a measure of length.

Two waves are traveling in a medium and arrive at a location at the same time. A. constructive interference B. destructive interference C. interference D. reflection

C. interference

How are the height of a person and the color of his automobile related? A. inversely B. directly C. unrelated

C. unrelated. Generally, a person's age and car color have no relation to each other.

How many liters are contained in 80 ml of fluid? A. 8 B. 80 C. 0.008 D. 0.080

D. 0.080

How many centimeters are in 3 meters? A. 1/300 B. 1/3 C. 3 D. 300 E. 3000

D. 300. Centi means hundredth. There are 100 centimeters in 1 meter. Thus, there are 300 cm in 3 meters.

The direction of motion of a particle in wave is perpendicular to the direction of propagation of the wave. What type of wave is this? A. Iongitudinal B. acoustic C. mechanical D. transverse

D. A characteristic of transverse waves is that the direction of propagation is perpendicular to the direction of particle motion in the wave. Sound waves are not transverse, but rather longitudinal.

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.

A sonographer adjusts the output power of the wave emitted by the transducer. Which of the following also changes? (More than one answer may be correct.) A. pulse repetition period B. PRF C. propagation speed D. intensity

D. As a sonographer adjusts the output power, the intensity will change. The PRF and pulse repetition period will change only when the maximum imaging depth (also called depth of view) changes. The sound's propagation speed will change only if the medium changes.

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 diagnostie imaging range from megahertz or 2 to 15 million approximately 2 to 15 second. cycles per

As a general rule, which of the following lists media in increasing order of propagation speeds? A. gas, solid, liquid B. liquid, solid, gas C. solid, liquid, gas D. gas, liquid, solid

D. Generally, sound travels slowest in gases, faster in liquids, and fastest in solids.

The letters below represent the abbreviations for the prefixes of the metric system. Select the sequence that appears in decreasing order. A. m, k, M, g, da B. g, m, k, d, p C. g, k, di, m, p, n D. M, k, da, d, c

D. M stands for mega and means "millions." k stands for kilo and means "thousands." da stands for deca and means "tens." d stands for deci and means "one-tenth." c stands for centi and means "one-hundredth." Thus, this sequence is of decreasing numbers.

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 the new pressure? A. three times larger than the original B. one third of the original C. six times more than the original D. unchanged

D. Pressure is defined as an amount of loloe divided by the area to which it is applied. It time, the area over which it is applied is the applied force is tripled, and at the same tripled, then the pressure remains unchanged.

Which of the following describes the characteristics of a sound wave? A. longitudinal, non-mechanical B. mechanical, transverse C. transverse, acoustic D. mechanical, longitudinal

D. Sound is a mechanical, longitudinal wave. A mechanical wave, such as sound, actually imparts energy to the molecules of the medium through which it travels. The molecules of the medium vibrate, striking their neighbors, which in turn vibrate. This chain reaction results in the acoustic energy traveling through the medium.

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.

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: A. doubled B. halved C. quartered D. four times larger

D. The intensity rises to four times its original value. Intensity is equal to power divided by beam area. In this case, the power is doubled and the area is halved. For example, if the original power was 4 watts and the initial beam area was 4 cm2, then the starting intensity was 4 watts divided by 1 and the final intensity has increased fourfold. intensity is 4 watts/cm2, the 4 watts/cm?. Since the initial intensity is 8 watts divided by 2 cm2, or area is halved, from 4 to 2 cm. The new doubled from 4 to 8 watts and the beam 4 cm?, or 1 watt/cm2. Now, the power is intensity was

What is the reciprocal of 1/8? A. 80 B. 10 C. 1 D. 8 E. 72

D. The reciprocal of 1/8 is 8.

What is the reciprocal of 100? A. 0.1 B. 100 C. 0.2 D. 0.01 E. 1/50

D. The reciprocal of 100 is 1/100 or 0.01.

What is the propagation speed of a 5 megahertz sound wave in soft tissue? A. 1,450 meters per sec B. 1,540 km/sec C. 1.54 m/s D. 1.54 mm/us

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

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

The volume of a cystic structure is sonographic data. Which estimated from of the following is an measurement of this volume? acceptable A. 6 B. 6 cm C. 6 cm? D. 6 cm3

D. The units of volume are length cubed, such as ft or cubic centimeters. Volume may also be expressed as length to the third power. A has no units, whereas B and C have units of length and area.

How are caloric intake and weight related? A. inversely B. partially C. reciprocally D. directly

D. These two terms are directly food intake increases, weight increases, related. As Similarly, as food intake decreases, weight decreases.

Ultrasound is defined aş 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, kHz or 0.02 MHz.

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

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

Which of the A. transverse, pressure waves following best describes sound waves? B. transverse, pressure waves out-of-phase longitudinal waves waves C. longitudinal, D. longitudinal,

D. longitudinal, pressure waves

All of the following are measures of length except: A. mile B. inch C. mm D. second E. km

D. second. Seconds are units of time, not length.

Which of the following terms does not belong with the others? A. compression B. region of high density C. region of high pressure D. wide molecular spacing

D. wide molecular spacing

How are the size of a tree and its age related?

Directly. Generally, as a tree ages, its size increases.

What is the wavelength of a wave with an unknown frequency traveling in soft tissue? A. 0.51 us 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.

How many milliliters are in 8 liters? A. 1/8 B. 8 C. 80 D. 800 E. 8000

E. 8000. Milli means thousandth. One liter contains 1,000 milliliters. Thus, 8 liters contain 8,000 ml. With questions such as this, as the metric prefix gets smaller, the number must increase. When the metric prefix gets larger, the number must decrease.

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 informs us of 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 is an appropriate unit for area? A. seconds B. yards C. inches D. cm3 E. square yards

E. square yards. Area is measured in units of length squared. The area that carpet covers is measured in square yards.

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. Propagation 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.

True or False? The wavelength of an acoustic wave is shorter when it is pulsed rather than continuous.

False. Wavelength cycle in a wave. reports the length of one The wavelength does not change based on whether the cycle is part of a pulsed or continuous wave.

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.

What is the name of the horizontal axis of a graph? A. z-axis В. х-ахis C. y-axis D. red axis

The horizontal axis of a graph is the x-axis. The x-axis extends side to side.

What is the vertical axis of a graph called? A. z-axis В. х-ахis C. y-axis D. time-axis

The vertical axis of a graph is called the y-axis and extends up and down.

True or False? Acoustic parameters are used to describe the features of sound waves.

True

True or False? Acoustic variables allow us to determine which waves are sound waves and which are not.

True

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

True. Although operators cannot change all the characteristics of an ultrasound beam produced by an individual transducer, they can change the initial power. As the operator increases the output power of a transducer, the initial intensity increases.

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

True. As stated above, 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 heard by humans.

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

True. The sonographer can adjust the strength of the ultrasound signal that a transducer creates. When a sonographer the output power, the electrical voltage increases sent to the transducer is increased. This produces a more violent vibration of the piezoelectric crystal within the transducer and, in turn, a stronger ultrasound wave.

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!

True or False? Shorter wavelength sound creates higher quality images with greater detail,

True. Wavelength plays a very important roie image quality. Shorter wavelength (higher frequency sound) produces higher quality images with greater detail.

What are the units of: • wavelength • frequency intensity propagation speed period power

Units are as follows: millimeters hertz • Watts/cm? meters/second • second Watts

The final amplitude of an acoustic of its original value. the original power. wave is reduced to one-half The final power is A. the same as B. one-half C. double D. none of the above

of a wave are D. Changes in the power proportional to changes amplitude squared. One-half squared in the wave's When one-half equals one-quarter (1/2 x 1/2 = 1/4). of the wave's original amplitude remains, then only one-fourth of the original power remains.

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

per second approximately one mile per second. in soft tissue. This is C. Sound travels at a speed of 1,540 meters

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

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