Ultrasound Physics I Exam Questions and
Answers Distinction Scores
What do waves do? - -All waves carry energy from one location to another
- How does sound travel? - -Sound travel through a medium, where
molecules are alternately compressed (condensed) and decompressed
(rarefied)
- What is condensation? - -Condensation (or compression) is where there is
a higher concentration of energy
- What is rarefaction? - -Rarefaction (or decompression) is where the energy
is more widely dispersed
- What kind of wave is a sound wave? - -Sound travels in a straght line.
Sound waves are longitudinal
- What do positive peaks represent on a graph? - -Condensation
- What do troughs represent on a graph? - -Rarefaction
- What determines sound's category? - -The frequency of the sound or the
number of cycles per second
- What is Infrasound? - -frequencies below 20HZ
- What is audible sound? - -Frequencies between 20 HZ and 20,000 HZ
- What is ultrasound? - -Frequencies above 20,000 HZ
- What is diagnostic Ultrasound? - -Frequencies above 1,000,000 HZ
(1,000 KHZ, 1 MHZ)
- What is the sound velocity of soft tissue? - -1540 m/sec
or 1.54 mm/msec
- What properties determine the velocity through a material? - -The
material's stiffness and density
- What will a little increase in stiffness do to velocity? - -Cause a significant
increase in velocity
, - What will an increase in density result in? - -An increase in density will
result in a slight decrease of the velocity.
- How does an increase in stiffness affect velocity? - -Materials that are stiff
have a significantly higher velocity of sound
- How does frequency affect the velocity of sound? - -The velocity of sound
is NOT affected by frequency.
- How does a transducer work? - -A transducer converts one form of energy
into another. It converts electrical energy into mechanical energy and back
into electric energy
- What is a piezoelectric element - -A piezoelectric element, typically a
crystal or a man made ceramic unit, is an element that, when acted upon by
energy, will vibrate and produce mechanical energy
- What is the typical force applied to the element? - -100 volts
- What is pressure? - -Pressure is the amount of force per unit area
- How is pressure measured? - -in Pascals
- What is nomial resonant frequency? - -the number given to the transducer
(ie a 3.5)
- What affects the resonant frequency? - -The thickness of the element.
- How does a thinner element affect resonant frequency? - -The frequency
will be higher
- How does a thicker element affect resonant frequency? - -The frequency
will be lower
- Describe Huygens Principle - -Sound waves produced by the imaging
transducer originate at multiple points on the surface of a piezoelectric
element. Each of these waves produce wavelets that project off of the
waves, and each wavelet has its own wavelets.
- What are broadband transducers? - -Broadband (or multi hertz)
transducers can be operated to produce ultrasound pulses equal to one of
multiple selected frequencies. The 3.5 MHz transducer, for example, can be
operated at 2 MHz, 3.5 MHz or 5 MHz
Answers Distinction Scores
What do waves do? - -All waves carry energy from one location to another
- How does sound travel? - -Sound travel through a medium, where
molecules are alternately compressed (condensed) and decompressed
(rarefied)
- What is condensation? - -Condensation (or compression) is where there is
a higher concentration of energy
- What is rarefaction? - -Rarefaction (or decompression) is where the energy
is more widely dispersed
- What kind of wave is a sound wave? - -Sound travels in a straght line.
Sound waves are longitudinal
- What do positive peaks represent on a graph? - -Condensation
- What do troughs represent on a graph? - -Rarefaction
- What determines sound's category? - -The frequency of the sound or the
number of cycles per second
- What is Infrasound? - -frequencies below 20HZ
- What is audible sound? - -Frequencies between 20 HZ and 20,000 HZ
- What is ultrasound? - -Frequencies above 20,000 HZ
- What is diagnostic Ultrasound? - -Frequencies above 1,000,000 HZ
(1,000 KHZ, 1 MHZ)
- What is the sound velocity of soft tissue? - -1540 m/sec
or 1.54 mm/msec
- What properties determine the velocity through a material? - -The
material's stiffness and density
- What will a little increase in stiffness do to velocity? - -Cause a significant
increase in velocity
, - What will an increase in density result in? - -An increase in density will
result in a slight decrease of the velocity.
- How does an increase in stiffness affect velocity? - -Materials that are stiff
have a significantly higher velocity of sound
- How does frequency affect the velocity of sound? - -The velocity of sound
is NOT affected by frequency.
- How does a transducer work? - -A transducer converts one form of energy
into another. It converts electrical energy into mechanical energy and back
into electric energy
- What is a piezoelectric element - -A piezoelectric element, typically a
crystal or a man made ceramic unit, is an element that, when acted upon by
energy, will vibrate and produce mechanical energy
- What is the typical force applied to the element? - -100 volts
- What is pressure? - -Pressure is the amount of force per unit area
- How is pressure measured? - -in Pascals
- What is nomial resonant frequency? - -the number given to the transducer
(ie a 3.5)
- What affects the resonant frequency? - -The thickness of the element.
- How does a thinner element affect resonant frequency? - -The frequency
will be higher
- How does a thicker element affect resonant frequency? - -The frequency
will be lower
- Describe Huygens Principle - -Sound waves produced by the imaging
transducer originate at multiple points on the surface of a piezoelectric
element. Each of these waves produce wavelets that project off of the
waves, and each wavelet has its own wavelets.
- What are broadband transducers? - -Broadband (or multi hertz)
transducers can be operated to produce ultrasound pulses equal to one of
multiple selected frequencies. The 3.5 MHz transducer, for example, can be
operated at 2 MHz, 3.5 MHz or 5 MHz
