Physics- PW & CW Review for Exam
Pulse Repetition Period is affected by
both on time and off time
As "averaging (listening) time" increases, the corresponding average intensity
decreases
As ultrasound frequency is increased, pulse duration:
decreases
If the amplitude of a wave is decreased by 3 times, what happens to the wave intensity?
decreases by 9 times
Select the TWO characteristics of a medium that primarily determine its speed of sound.
density stiffness
This set of waves will result in [answer] interference.
destructive
Hours worked and take-home pay are [answer] related.
directly
Power is [answer1] related to intensity and [answer2] related to amplitude.
directly and directly
What is transferred from one location to another as a wave propagates?
energy
Which wave parameter describes the number of cycles that pass a given point in one second?
frequency
Which of the following characteristics will produce the slowest speed of sound?
high density, low stiffness
Short pulses are better for ultrasound imaging because:
image sharpness improves
Select TWO examples of units of length
inches millimeters
As peak ultrasound intensity increases, the pulse-average and time-average intensities tend to
increase
If a wave's amplitude is quadrupled, the wave's intensity will [answer1] [answer2] times its original value.
increase 16 times
As pulse duration is increased, spatial pulse length:
increases
If all other factors remain the same, what happens to the duty factor when a transducer with longer pulse duration is used?
increases
If all other factors remain the same, what happens to the duty factor when the image depth is decreased from 8 cm to 5 cm?
increases
If the power of a wave is increased by 3 times, what happens to the wave intensity?
increases by 3 times
The wave parameter that describes the concentration of energy in a sound beam is:
intensity
The following sentence is best defined as:"More than one wave losing their individual characteristics and combining, at that moment, to form a single wave."
interference
Two waves are traveling in a medium and arrive at the same location at the same time. What event definitely takes place?
interference
An example of a/an [answer] relationship is the link between caffeine and drowsiness.
inverse
How are hours of sleep and drowsiness related?
inversely
Select TWO examples of units for area
kilometer^2 feet^2
Select TWO examples of units for volume.
meter^3 yard^3
A 5 MHz ultrasound beam travels through a medium at a speed of 1500 m/s? This medium is most likely:
milk
Appropriate units of SPL are:
mm
Appropriate units of pulse duration are:
ms
An individual's hand size and their favorite car are [answer] related.
not
The beam uniformity coefficient involves the average intensity of the ultrasound beam
over the beam area
With regard to intensities, [answer] is always larger.
peak
Which parameter of a wave describes the amount of time it takes to complete one cycle?
period
The rate of energy transfer, or the rate at which work is performed is ____.
power
If the amplitude of a wave is halved, what happens to the wave power?
power is quartered
The relationship between PRP and PRF is best described as
reciprocal
"Mechanical energy transmitted by pressure waves in a material medium." can best be defined as:
sound
If all other factors remain the same, what happens to the duty factor as the ultrasound pulse travels from a medium with high sound speed to one with much lower speed?
stays the same
Which wave parameter describes the distance from the beginning to the end of one complete cycle?
wavelength
Which of the following are considered acoustic variables?
-distance -pressure -density
A 2.25 MHz, three-cycle pulse of ultrasound is emitted at a pulse repetition frequency of 500 pulses per second. What is the approximate percent duty factor?
.067%
A 4.5 MHz ultrasound beam will have a period of approximately:
0.2 us
What is the wavelength of 5MHz in soft tissue?
0.3 mm
What is the percent duty factor for a pulse echo beam having a 3 μs pulse duration and a 900 μs pulse repetition period?
0.3%
In soft tissue, what is the approximate period of a 2.25 MHz ultrasound pulse
0.4 us
If pulse duration is 0.5 µs, and pulse repetition period is 100 µs, what is the duty factor?
0.5%
Utilizing the values determined for PD and PRP, what is the duty factor of a system emitting a five-cycle, 1 MHz ultrasound pulse with a PRF of 1000 pulses per second, calculate the duty factor.
0.5%
What is the wavelength of a 2.5 MHz ultrasound beam having a velocity of 1520 m/s in soft tissue?
0.61 mm
A 2.25 MHz three-cycle pulse of ultrasound is emitted at a pulse repetition frequency of 500 pulses per second. What is the approximate wavelength in soft tissue?
0.68 mm
The wavelength of a 2.25 MHz ultrasound beam in soft tissue is:
0.7 mm
When period and frequency are multiplied, the result is [answer].
1
Which pulse has a pulse repetition period of 1 ms?
1 kHz
What is the period of the earth's rotation around the sun?
1 year
What is the duty factor of a continuous ultrasound beam?
1.0
1.54 mm/ us = [answer] km/s
1.54
A parameter associated with a sound wave is the speed at which it travels through a given medium. What is the acoustic speed of ultrasound in soft tissue?
1.54 mm/us
What is the approximate wavelength range for diagnostic ultrasound?
100 to 1000 um
Five cycles of 1 MHz ultrasound are emitted per pulse with a pulse repetition frequency of 1000 pulses per second. What is the pulse repetition period?
1000 us
Approximately how far will sound travel in soft tissue in 10 μs?
15 mm (d = 1.54mm/us * 10 us) =15.4 mm
A sound beam has a wavelength of 2 mm and a period of 1.0 ms. What is the sound speed?
2 m/s
Although up to 18 MHz can be used for superficial imaing, typical ranges for diagnostic imaging are [answer1] MHz to [answer2] MHz.
2 to 20 Mhz
Using the derived answer for wavelength (.68 mm) in the previous question, what is the approximate spatial pulse length in soft tissue?
2.05 mm
Five cycles of 2 MHz ultrasound are emitted per pulse. What is the approximate pulse duration?
2.5 us
Ultrasound is defined as sound having a frequency above [answer] Hz.
20,000 Hz
T/F: In a transverse wave, particles move in the same direction the wave propagates.
False
T/F: Sound can travel in a vacuum.
False
Given the equation: Fd = 2 V Ft Cos < / cSolve for: Cos < = [answer]
Fd*c/2*V*Ft the original equation solves for Doppler shift
Pressure in a compressed wave is [answer].
High
Which of the following best describes sound waves?
Longitudinal waves; requires a medium
Which parameter is a measure from the middle value to the maximum (or minimum) value of a wave?
amplitude
cm^2 is an appropriate unit of
area
What is the approximate frequency of ultrasound that has a wavelength of 0.4 mm in soft tissue?
3.8 MHz
24 cm/min. = [answer] mm/sec
4
Five cycles of 1 MHz ultrasound are emitted per pulse with a pulse repetition frequency of 1000 pulses per second. What is the pulse duration?
5 us
How many Hertz is 5 kHz?
5,000 Hz
5 W/cm 2 = [answer] mW/mm 2
50
50 cm = [answer] mm
500
How many days are in a minute? (Hint: This should be a small value!) (Do on paper)
6.9*10^-4
What is the approximate speed of sound if the wavelength is 0.2 mm and a 3 MHz ultrasound beam is used?
600 m/s
7.5 MHz = [answer] Hz
7,500,000 Hz
What is the approximate wavelength of 2 MHz in soft tissue?
800 um
A 5 μs pulse is emitted every 500 μs. What is the pulse repetition period (PRP)?
= 1/ frequency =1/.002 = .5 ms
Which of the lines in the graph represent a direct relationship?
B
Which of the following best describes wave A and C?
Out of phase, will interfere destructively
A 5 μs pulse is emitted every 500 μs. What is the pulse repetition frequency (PRF)?
PRF= 1/500 us =.002/us
Which is an acceptable unit for pressure?
Pa
The smallest intensity measurement is
SATA
The largest intensity measurement is:
SPTP
If the frequency of a wave increases, the propagation speed: (The medium does not change.)
Stays the same
This set of waves will result in [answer] interference.
constructive
When waves of different frequencies interact, which kind of interference results?
constructive and destructive
