DMS Physics Midterm Flashcards
What are the acoustic variables?
Pressure (Pa)
Density (kg/cm3 )
Distance (cm, feet, mile)
The effects of the medium upon the sound wave is called
Acoustic propagation properties
____ is the time to complete one cycle
Pulse duration
pulse period
period
duration period
Period
____ is the distance covered by one cycle
pulse length
wavelength
cycle distance
cycle duration
Wavelength
Propagation speed = ____ X wavelength
Frequency
A sound wave’s frequency is 10 MHz. The wave is traveling in soft tissue. What is its wavelength?
- 15 mm
- 54 mm
- 4 mm
- 77 mm
10 MHz
0.15 mm
wavelength = (1.54 mm/μs) / (frequency MHz)
If the frequency of an ultrasound wave is doubled what happens to the period?
Doubles
halved
remains the same
4 times greater
halves
Period and frequency = inversely related
The units of pulse repetition frequency are:
per second
msec
mm/μ
MHz
Per second (or Hz)
The tie from the beginning of a pulse until its end is ____
Pulse duration
What happens to the speed of sound in a medium when the bulk modulus of the medium increases?
Faster
If a wave’s amp is doubled, what happens to the power?
Quadrupled
Power of sound has units of ?
watts
The duty factor for continuous wave US is:
10.0
1%
- 0
- 0%
1.
What are the units of intensity?
Watts/ cm2
What happens to the speed of soundi n a medium when the bulk modulus of the medium decreases?
Slower
A pulse is emitted by a transducer and is traveling in soft tissue. The go-return time, or time of flight, of a sound pulse is 130 microseconds. What is the reflector depth?
10 cm
10 mm
10 m
130 mm
13 cm
10 cm
The rayl is the unit of
Impedance
Impedance is the ____ of ____ and ___
Product, propagation speed, density
Attenuation’s three components
Scattering, reflection, absorption
As the impedances of two media become vastly different the
Reflection increases
transmission increases
refraction increases
absorption increases
Reflection increases
The angle between an ultrasound pulse and the boundary between two media is 90 degrees. What is this called?
Orthogonal incidence
Refraction only occurs if:
There is an oblique incidence (other than 90 degrees) and different propagation speeds
With normal incidence, what factors affect refraction of ultrasound?
Propagation speeds
frequencies
attenuation coefficient
none
None
With right angle incidence, reflections are always generated at a boundary if the propagation speeds of the media are different.
T or F
False
___ is a redirection of ultrasound in many directions as a result of a rough boundary between two media
Scattering
Snell’s lay describes physics of ___
Refraction
The sonographer cannot change, directly or indirectly, the duty factor of an ultrasound machine
T or F
false
What has the greatest amound of attenuation?
Bone
fat
water
muscle
bone