Part 2: Physics Principles Flashcards
The mass you are imaging has a diameter of 35 mm. This value can also be expressed as: ____cm
3.5
Relative measurement of intensity based on a logarithmic scale is expressed in:
Decibels
Which prefix equals 10 -3?
a. mico
b. milli
c. mega
d. centi
e. none of the above
b
When you change the transmit frequency, which of the following is altered?
a. displacement amplitude of the particles in the medium
b. speed at which the sound wave propagates through the medium
c. number of cycles per second
d. Pulses transmitted per second
e. number of electric impulses applied to the transducer per second
c
While performing a Doppler ultrasound examination, you adjust the pulse repetition frequency to 12 kHz. This can also be expressed as:
a. 0.12 Hz
b. 1200 Hz
c. 1.2 MHz
d. 12,000 Hz
e. 120 MHz
d
In sound wave propagation, a region of elevated pressure is termed:
compression
When you switch from a 2.5 MHz to a 5.0 MHz transducer, the sound wavelength:
halves
Wavelength depends on what two factors?
frequency and propagation speed
Which of the following human tissues has the highest rate of attenuation of an ultrasound wave?
a. liver
b. fat
c. fluid
d. lung
e. blood vessels
d
The propagation speed for sound is lowest in which of the following biologic tissues?
a. fat
b. blood
c. muscle
d. bone
e. liver
a
Which of the following factors does NOT affect impedance?
a. stiffness
b. density
c. propagation speed
d. frequency
e. all of the above affect impedance
d
You are imaging a structure containing two media having the same acoustic impedance. What will occur at the boundary of the two structures?
all of the sound will be transmitted
What is the purpose of the gel coupling between the transducer and the skin?
to provide a medium for sound transmission, since ultrasound does not propagate through air
The unit of impedance is the:
Rayl
With absorption, acoustic energy is converted to:
heat
The intensity transmission coefficient at the interface between two structures equals 1/100. What is the intensity reflection coefficient?
99/100
Which of the following is an example of a Rayleigh scatterer?
a. renal capsule
b. arterial wall
c. red blood cell
d. bowel gas
e. femur
c
In order to display a structure on your sonographic image, the sound beam must be reflected at the interface. What is required for sound reflection at the interface of two structures?
a difference in the acoustic impedance of the media
An example of a specular reflector is:
a. pericardium
b. liver parenchyma
c. red blood cells
d. ascites
e. hematoma
a
What system control can you adjust to compensate for the effect of sound attenuation in the body?
TGC
While imaging a cyst, you notice shadowing posterior to each lateral border of the cyst. What is the source of the shadows?
bending of the sound beam due to different media propagation speeds
The algebraic summation of waves leading to patterns of minima and maxima is called:
interference
An interaction of echoes that leads to reinforcement rather than to partial or total cancellation is known as:
constructive interference
Which phenomenon is associated with a pattern produced by a sound beam after passing through a small aperture?
diffraction
What sound parameter is determined only by the medium?
propagation speed
Snell’s law describes:
a. the percentage of reflection at an interface with normal incidence and different densities
b. the angle of sound transmission at an interface between media having different propagation speeds
c. the amount of attenuation of sound in tissue with depth
d. the amount of backscatter from a diffuse reflector
e. The angle of sound reflection at an interface with oblique incidence and nonspecular reflection
b
As a general observation about media in diagnostic sonography, sound propagates faster in materials with greater:
stiffness
During the performance of a sonographic examination you would be most likely to encounter refraction in this view:
curved interface
You may observe sound attenuation by all of the following EXCEPT:
a. reflection
b. scattering
c. conversion of sound to heat
d. absorption
e. compression
e
When you image sound reflected from a large, smooth interface, you are observing results of:
specular reflection
During a sonographic examination of a large vessel, a 45 degree beam-to-vessel angle would be called:
oblique incidence
What occurs when you image a structure with oblique incidence?
The angle of reflection will be oriented away from the transducer, resulting in decreased visualization of the structure
Which of the following statements regarding the effect of frequency on Rayleigh scattering is TRUE?
a. the amount of scattering is not affected by frequency
b. scattering intensity doubles if frequency is doubled
c. doubling the frequency results in halving the scattering intensity
d. doubling the frequency results in quartering the scattering intensity
e. scattering intensity is proportional to frequency raised to the fourth power
e
An echo from which one of the following sound reflectors is most dependent on the angle of incidence?
a. Rayleigh scatterer
b. diffuse reflector
c. specular reflector
d. acoustic scatterer
e. nonspecular reflector
c
What determines acoustic impedance?
density and propagation speed of the medium
Diagnostic ultrasound is limited in its diagnostic application to the adult brain because:
a. the speed of sound in the brain is much faster than that in soft tissue, resulting in a range artifact.
b. nearly all of the sound is transmitted at the interface between bone and soft tissue with no reflection to create an image
c. diffraction of the sound beam occurs because of the irregular surface of the brain, resulting in little transmission of sound through the cranial interface
d. bending of the sound beam due to refraction results in a multipath artifact that distorts the image, making it nondiagnostic at high frequencies
e. the great acoustic impedance mismatch between the cranium and soft tissue causes most of the sound to be reflected at that interface
e
Which of the following describes diffuse reflection?
a. the reflected beam is scattered in various directions
b. the reflected frequency is altered by the Doppler effect
c. The reflected beam is amplified by the focusing effect of scatterers
d. the reflected beam is weaked by the large acoustic impedance mismatch at the tissue interface
e. There is no reflection at a tissue interface because of a disorganized transmit beamj
a
According to Snell’s law, the angle of transmission is related to the incident beam angle and:
the relative speeds of sound in the two media
Which of the following interactions of sound and tissue decreases the intensity of the transmitted beam?
a. absorption
b. reflection
c. scattering
d. conversion of sound to heat
e. all of the above
e
What is the relationship of frequency to absorption?
If frequency is doubled, absorption is doubled
What term is used to describ the reduction in the intensity of sound as it propagates through tissue?
attenuation
Another term for nonspecular reflection is:
scattering
While performing a sonographic exam, you encounter the following interfaces. Which will produce the weakest reflected signal?
a. organ parenchyma/fluid
b. organ parenchyma/air
c. organ parenchyma/organ parenchyma
d. organ parenchyma/bone
e. organ parenchyma/ligament
c
During a diagnostic ultrasound examination, you encounter all of the interactions of ultrasound and tissue listed below. Which one will NOT cause a redirection of part of the ultrasound energy?
absorption
As you perform a sonographic exam, you switch from a 3.5 MHz transducer to a 7.0 MHz transducer to image a superficial structure. Compared to the 3.5 MHz transducer, what will the 7.0 MHz attenuation rate and wavelength be?
double the attenuation rate, one-half the wavelength
You are scanning a large mass that is composed primarily of fat. Which of the following are you most likely to encounter?
a. Posterior acoustic shadowing caused by increased attenuation through the fat
b. axial misregistration of objects distal to the mass on the screen due to the slower propagation speed through fat
c. Lateral misregistration of the mass on the screen because of refraction
d. total reflection of the sound beam caused by a large acoustic impedance mismatch
e. diffraction of the sound beam due to a virtual small aperture through the mass
b
What two conditions must be present to cause refraction of a sound wave?
perpendicular incidence and identical media propagation speeds
The transducer you are using transmits wide-bandwidth pulses whose frequency content is 2-5 MHz. Which of the following most correctly describes the reflected echo signals after they have traversed the tissue?
a. the echo signals will be shifted down in frequency due to the increased attenuation of higher frequencies
b. the echo signals will be of reduced intensity but will have the same frequency content as the transmitted beam
c. the echo signals will be shifted upward in frequency due to the increased absorption of the lower frequencies
d. only the center frequency component of the bandwidth will be reflected back to the transducer
e. the echo signal frequency content will be identical to that of the transmitted beam
a
When the sound beam is refracted during a sonographic examination, which of the following might you detect on the ultrasound image?
a. axial misregistration
b. lateral misregistration
c. reverberations posterior to a reflector
d. enhancement of a reflector
e. electrical interference
b
During production of a sonogram, you image the following structures. Which is the MOST attenuating?
a. blood
b. bile
c. soft tissue
d. calcification
e. muscle
d
What can you do to enhance the visibility of a specular reflector?
scan with perpendicular incidence
Whar interaction of ultrasound and tissue is primarily responsible for imaging the internal structure of organs?
scattering
What sound-tissue interaction is necessary to form an ultrasound image?
reflection
For soft tissue, on of the factors responsible for determining acoustic impedance is:
a. attenuation
b. frequency
c. absorption
d. density
e. amplitude
d
When you image a structure that is a specular reflector, the strength of the received signals depends on the following two factors:
a. difference in acoustic impedance and angle of incidence
b. difference in acoustic velocity and interface size
c. difference in acoustic velocity and motion of reflector
d. angle of incidence and tissue temperature
e. bulk modulus and interface size
a
Attenuation of the sound beam increases with increasing:
a. path length
b. absorption
c. frequency
d. scattering and reflection
e. all of the above
e
You are imaging a round mass with irregular borders. The mass has a much slower propagation speed than surrounding tissue. What sound-tissue interaction will be encountered as the ultrasound propagates through this interface?
a. refraction
b. reflection
c. absorption
d. scattering
e. all of the above
e
You are imaging a structure that is highly attenuating. Which imaging effect do you expect to encounter?
a. enhancement
b. increased penetration
c. shadowing
d. refraction
e. increased acoustic speckle
c
When you are educating your patient about the sonographic exam, sound travels through air from your mouth to your patient’s ears. Which of the following is true regarding the speed of sound travel through air?
a. the speed of sound in air is greater than the speed of light
b. the speed of sound in air is greater than the speed of sound in soft tissue
c. the speed of sound in air is not predictable
d. the speed of sound in air is slower than the speed of sound in soft tissue
e. the speed of sound in air is equal to the speed of sound in soft tissue
d
You have increased the transmit power while performing a pelvic ultrasound examination. This action increases which of the following?
a. penetration
b. acoustic power
c. image brightness
d. voltage applied to the transducer elements
e. all of the above
e
If sound waves of 3 MHz, 5 MHz, and 10 MHz are transmitted through the same section of anatomy, reflections from which frequency would reach the transducer first?
Reflections from all three frequencies would have nearly identical transit times
What would you do if the image does not show adequate penetration and the far field displays noise instead of tissue?
decrease transmit frequency
For pulsed ultrasound, which of the following factors determines the frequency of the sound wave?
a. pulse repetition frequency (PRF)
b. Transmitter frequency
c. area of the transducer elements
d. pressure applied to the transducer
e. all of the above
b
You have decreased the acoustic power by -3dB. Which of the following most accurately describes this adjustment?
a. the intensity has been quadrupled
b. the intensity has been quartered
c. the intensity has been increased 10 times
d. the intensity has been halved
e. the intensity has not been altered
d
Which of the following describes sound propagation through a vacuum?
a. sound travels as transverse waves through a vacuum
b. when sound travels through a vacuum, the propagation speed increases to 3,300,000 m/s
c. sound travels at the speed of light in a vacuum
d. sound propagation is random in a vacuum
e. sound cannot travel through a vacuum
e
when your patients asks you how much longer the ultrasound test will take, his voice is in the audible frequency range. Which of the following frequencies is in the audible frequency range?
a. 100 MHz
b. 10 kHz
c. 10 Hz
d. 10,000 MHz
e. 1,000,000 Hz
b
The maximum cyclical change in a quantity is known as:
amplitude
Bulk modulus is closely related to which of the following quantities?
a. attenuation
b. frequency
c. wavelength
d. volume
e. stiffness
e
Which most correctly describes sound propagation in a medium?
a. in sound propagation, a molecule travels from one end of the medium to antoher
b. Molecules oscillate back and forth to propagate sound waves but do not move from one end of the medium to another
c. A molecule does not vary its position as a sound wave travels
d. each molecule expands and contracts to propagate a sound wave through a medium
e. sound waves cannot travel through a medium
b
Which of the following terms denotes the time it takes for one cycle to occur?
a. frequency
b. amplitude
c. wavelength
d. period
e. pressure
d
If the number of cycles in a pulse is increased but the wavelength remains the same, which of the following is true?
a. the frequency is increased
b. the propagation speed is increased
c. the pulse duration is increased
d. the period is decreased
e. the bulk modulus is decreased
c
Which of the following is most likely also to decrease beam intensity?
a. increasing acoustic output
b. decreasing receiver gain
c. increasing focusing
d. increasing beam area
e. increasing amplitude
d
Which of the following best characterizes an ultrasound wave in human tissue?
a. mechanical longitudinal wave
b. radioactive wave
c. transverse rarefacetional wave
d. electromagnetic wave
e. electronic piezoelectric wave
a
The regions of low pressure and density that are formed during sound propagation are termed:
a. compressions
b. shear waves
c. rarefactions
d. cavitation
e. bulk modulus
c
The sound propagation speed used to calibrate range-measuring circuits on diagnostic sonography instruments is:
1540 m/s
Which of the following properties would result in increased propagation speed of sound through a medium?
a. increased stiffness
b. increased density
c. increased frequency
d. increased distance
e. increased amplitude
a
Which of the following frequencies is considered to be ultrasound?
a. 2000 Hz
b. 20 Hz
c. 2 MHz
d. 200 Hz
e. 2 Hz
c
You are performing a sonographic exam on a large patient. Which transducer would provide the least amount of signal attenuation?
a. 2.5 MHz
b. 3.5 MHz
c. 5.0 MHz
d. 7.5 MHz
e. 10 MHz
a
Which of the following increases as frequency increases?
a. absorption
b. scattering
c. attenuation
d. a and c only
e. all of the above
e
What is the velocity of an ultrasound wave in bone?
4080 m/s
The speed of sound is defined as the:
speed at which sound propagates through the medium
A longitudinal wave is characterized by:
particle motion occurring in the same direction as propagation
Wavelength is measured in:
millimeters
What terms refers to regions of decreased particle density in a sound beam?
rarefaction
10^-3 equals:
1/1000
Which of the following represents the number 1234 in scientific notation?
a. 0.1234
b. 0.1234 x 10^3
c. 1234 x 10^1
d. 1234 x 10^-1
e. 1.234 x 10^3
e
One MHz equals:
a. 10^3 Hz
b. 10^-3 Hz
c. 10^6 Hz
d. 10^-6 Hz
e. 10^9 Hz
c
Terms used to describe the strength of the sound beam include:
a. amplitude and impedance
b. amplitude and wavelength
c. amplitude and intensity
d. intensity and impedance
e. frequency and impedance
c
You are imaging with a 5MHz linear array transducer. What sound parameter stays constant as the beam propagates through the tissue?
a. frequency
b. intensity
c. amplitude
d. wavelength
e. none of the above
e
Ultrasound propagation velocity depends on:
a. amplitude and frequency
b. impedance and attenuation
c. density and compressibility
d. dynamic range and compression
e. impedance and density
c
You notice that the image in the far field is less bright compared to the near field. This is due to:
a. sound attenuation
b. propagation speed variation
c. refraction
d. diffraction
e. The Doppler Effect
a
Acoustic impedance:
a. is independent of the speed of sound
b. is inversely proportional to the density
c. is greater in gas than in metal
d. equals density times the propagation speed
e. is independent of the density
d
What determines the speed of sound?
medium through which sound wave passes
You will NOT see refraction in the sonographic image if:
a. the sound beam strikes an interface at an angle of greater than 45 degrees
b. the sound beam is perpendicular to the interface
c. the sound beam is 45 degrees to the interface
d. the sound beam changes propagation speed at the interface
e. the sound beam strikes an interface at an angle of less than 45 degrees
b
The rate of sound attenuation is lowest in:
a. air
b. water
c. liver
d. bone
e. lung
b
When you perform a Doppler exam, the frequency of the transmitted signal is determined by:
a. backing material
b. attenuation factor of the tissue
c. bandwidth
d. the frequency of the electric signal applied to the transducer
e. amplitude
d
power divided by the beam area is equal to the:
intensity
axial resolution is determined chiefly by:
pulse duration
Choose two benefits of tissue harmonic imaging.
a. grating lobe artifacts are reduced and lateral resolution is improved
b. axial and lateral resolutions are improved
c. contrast and axial resolutions are improvfed
d. penetration is improved and axial resolution is improved
e. penetration is improved and contrast resolution is improved
a
Acoustic impedance increases with which of the following?
a. increased tissue density
b. increased propagation speed
c. increased transducer frequency
d. a and b
e. all of the above
d
When you adjust the pulse repetition frequency, you are changing:
the number of pulses per second
Which of the following would increase the spatial pulse length?
a. increased PRF
b. decreased number of transmit pulses per frame
c. increased number of transmit pulses per second
d. increased number of transmit pulses per line
e. increased number of cycles per pulse
e
Doppler pulses used for diagnostic purposes are typically _____ cycles long.
5-30
The time that it takes for one pulse to occur is known as the:
pulse duration
The length of space over which one cycle occurs is known as the:
wavelength
Bandwidth refers to:
range of frequencies in a pulse
When sound strikes a specular reflector at an oblique angle, the angle of reflection is:
equal to the angle of incidence
Which describes constructive interference?
a. sound waves are in phase and resulting amplitude is increased
b. sound waves are in phase and resulting amplitude is decreased
c. sound waves are out of phase and resulting amplitude is increased
d. sound waves are out of phase and resulting amplitude is decreased
e. none of the above
a
Which sound beam frequency would exhibit the greatest intensity loss with increasing depth?
a. 10 MHz
b. 8 MHz
c. 5 MHz
d. 3 MHz
e. 2 MHz
a
Interference patterns of reflected waves cause:
acoustic speckle
Attenuation of the sound beam is affected by:
a. absorption
b. scattering
c. reflection
d. propagation speed
e. a, b, and c
e
The transfer of acoustic energy into heat is termed:
absorption
The unit of sound intensity is the:
decibel
a way to express the ratio or comparison between two sound intensity levels
decibel
3 dB decrease represents ___%
50
6 dB decrease represents ___%
75
10^-6
micro
10^6
mega
10^-2
centi
10^3
kilo
sound propagates through tissue as a series of _____ and _____.
compressions
rarefactions
Wavelength is _________ to frequency.
inversely proportional
Doubling the frequency _____ the wavelength.
halves
equation for wavelength
propagation speed divided by frequency
______ increases if density or propagation speed increases.
impedance
Impedance is not affected by _____.
frequency
impedance equation
density times the speed of sound
For sound to be reflected, there must be a difference in ________ at the interface.
acoustic impedance
Normal incidence indicates a _____ degree angle of incidence.
90
The ________ describes the fraction of sound transmitted at a boundary.
intensity transmission coefficient
The _____ describes the fraction of sound reflected at a boundary.
intensity reflection coefficient
ITC + IRC always = ____
1
A ______ is an object that is much smaller than the wavelength of the sound beam.
rayleigh scatterer
Rayleigh scatterer in diagnostic ultrasound is the _____.
red blood cell
The edge shadowing seen with curved interfaces is caused by _____ of the sound beam.
refraction
A _______ is a large, smooth interface such as the renal capsule, diaphragm, or pericardium.
specular reflector
The ____ is used to amplify echo signals from deeper structures, which have undergone greater amounts of attenuation more than echo signals from shallow structures.
TGC
_______ is the general term for various phenomena in which waves from different parts of a source add or subtract.
diffraction
______ realtes the angle of transmission of the sound beam to the relative velocities of sound in the two media.
Snell’s law
______ of the sound beam requires sound reflection from a curved interface?
Refraction
______ includes all sound interactions that result in a weakening of the beam.
Attenuation
conversion of sound to heat in tissue
absorption
_____ results in a bending of the beam
refraction
Normal incidence is also known as _______.
perpendicular incidence
Normal incidence occurs when the sound beam strikes the interface at a ____ degree angle.
90
With specular reflectors, the angle of reflection is equal to the _______.
angle of incidence
If _______ most of the sound will be reflected back at the transducer.
perpendicular incidence
If ______ most of the sound will be reflected away from the transducer at an angle equal to that of the transmitted angle.
oblique incidence
______ is caused by a lower attenuation within the structure than in the surrounding tissue.
enhancement
_______ results from decreased attenuation through a fluid-filled structure compared to the adjacent tissue.
acoustic enhancement
Changes in _______ do not produce acoustic enhancement.
propagation speed
______ is determined by the density and propagation speed of the medium.
acoustic impedance
low frequencies enhance penetration that results in poor _______.
spatial resolution
With _____, the beam is weakened because of incoherence.
diffuse reflection
______ occurs when the sound beam strike a large, rough surface. The beam is reflected at many different angles because it strikes the rough surface at varying angles of incidence. This has the result of causing the reflected waves to be incoherent (out of phase_ with each other, weakening and defocusing the beam.
diffuse reflection
______ dictates the angle of transmission that will occur at an interface with refaction of the sound beam.
Snell’s law
Refraction of the sound beam will occur whenever there is _______ and different ______ between the two media.
oblique incidence
propagation speeds
______ occurs when the interface is large and smooth.
specular reflection
_______ or ______ occurs when the interface is small, less than several wavelengths across.
nonspecular reflection
scattering
Reflected signal strength depends on _______ mismatch.
acoustic impedance
______ contributes to attenuation but does not redirect the sound beam/
absorption
If frequency is doubled, the rate of attenuation is _____.
doubled
Because sound travels slower in fat than in soft tissue, a large mass composed primarily of fat may cause _______ of the objects distal to the mass on the ultrasound image.
axial misregistration
Reflector size does not affect ______.
refraction
______ does not occur with perpendicular incidence.
refraction
______ is a bending of the sound beam that results in lateral misregistration of structures posterior to the refracted beam.
Refraction
_____ depends on both oblique incidence and different media propagation speeds.
refraction
With specular reflectors, the anlg eof reflection is equal to the _______.
angle of transmission
______ and ______ give rise to the echo signals that are displayed on the monitor
reflection
scattering
equation for acoustic impedance
z=pc
The main factor determining acoustic impedance is changes in _____.
tissue density
The _____ of the reflected signal depends on the different in acoustic impedance between the two tissues.
amplitude
_______ reflection is highly angle dependent.
specular
The _______ is the degree of attenuation for each centimeter of sound propagation.
attenuation coefficient
______ occurs because of the oblique incidence and different propagation speeds of the insonated media.
Refraction
______ occurs because the acoustic impedance is different.
reflection
______ occurs as sound propagates through tissue.
absorption
______ occurs as a result of the irregular margins of the mass.
scattering
With increased ______, there will be a loss of sound energy through reflection, scattering, and absorption.
attenuation
air sound travel
300 m/s
soft tissue sound travel
1540 m/s
______ occurs when the sound strikes an irregular or rough surface that is small compared to the wavelength.
scattering
_______ occurs when the surface is smooth and large compared to the wavelength.
specular reflection
______ requires the sound to pass through a small aperture.
diffraction
______ occurs with oblique incidence and a change in propagation speeds at the interface.
refraction
The speed of sound does not vary appreciably with _____.
frequency
describes the number of cycles that occur in one second
frequency
determined by the medium, not the sound source
speed of sound
determined by the sound source, not by the medium
frequency
When penetration through tissue is inadequate and the far field demonstrates noise, lowering the _______ is a good option and may provide adequate penetration.
transmit frequency
The number of electric pulses delivered to the active element per second
pulse repetition frequency
An intensity change of 3 dB corresponds to a:
doubling of the intensity
If the intensity is changed by -3dB, then:
the intensity is halved
the physical movement of particles within a medium
propagation
What can sound not propagate through?
vacuum
The audible frequency rage
20 Hz to 20,000 Hz
In sound propagation, molecules oscillate back and forth, creating a series of ______ and _____.
compressions
rarefaction
period is _______ proportional to frequency.
inversely
Doubling the frequency, _____ the period
halves
the time it takes to complete one pulse
pulse duration
If the number of cycles in the pulse is increased, it will take ____ time for one pulse to occur.
more
how many cycles occur in one second
frequency
the speed at which sound travels through a particular medium
propagation speed
Period is ____ proportional to frequency.
inversely
the time is takes for one cycle to occur
period
related to media stiffness and helps to determine propagation speed
bulk modulus
For a given output power, the intensity is expected to fall if the beam area is ______.
increased
High pressure regions are _______.
compressions
low pressure regions are _______.
rarefactions
Propagation speed decreases with _____ density.
increased
Increasing distance will ____ the round-trip travel time but will not affect the rate of travel.
increase
Increasing ____ will increase the sound intensity but have no effect on propagation speed.
amplitude
Attenuation is ______ to frequency.
proportional
the time is take one complete cycle to occur
period
The _____ pulse will produce the better axial resolution
shortst
The _____ produces the greatest spatial pulse length.
longest
Particle motion that is perpendicular to the direction of propagation characterizes a ______.
transverse wave
The intensity and amplitude of the beam ____ as a result of attenuation.
decrease
the ______ is altered with the downshifting of the overall frequency bandwidth.
wavelength
weakening of beam strength
attenuation
bending of the sound beam
refraction
occurs whenever the beam strikes an interface where the propagation speed is different between two media and the angle of incidence is not perpendicular (oblique incidence)
refractioni
_______ transducers can be driven at different frequencies.
broad bandwidth
Unit for intensity
watts per meter squared (power per unit area)
The shorter the pulse duration, the _____ the axial resolution.
better
______ does not affect attenuation of the sound beam.
propagation speed
