DMS Physics Midterm

Question 1

What are the acoustic variables?

Answer 1

Pressure (Pa)

Density (kg/cm³ )

Distance (cm, feet, mile)

Question 2

The effects of the medium upon the sound wave is called

Answer 2

Acoustic propagation properties

Question 3

____ is the time to complete one cycle

Pulse duration

pulse period

period

duration period

Answer 3

Period

Question 4

____ is the distance covered by one cycle

pulse length

wavelength

cycle distance

cycle duration

Answer 4

Wavelength

Question 5

Propagation speed = ____ X wavelength

Answer 5

Frequency

Question 6

A sound wave’s frequency is 10 MHz. The wave is traveling in soft tissue. What is its wavelength?

0. 15 mm
1. 54 mm
2. 4 mm
3. 77 mm

10 MHz

Answer 6

0.15 mm

wavelength = (1.54 mm/μs) / (frequency MHz)

Question 7

If the frequency of an ultrasound wave is doubled what happens to the period?

Doubles

halved

remains the same

4 times greater

Answer 7

halves

Period and frequency = inversely related

Question 8

The units of pulse repetition frequency are:

per second

msec

mm/μ

MHz

Answer 8

Per second (or Hz)

Question 9

The tie from the beginning of a pulse until its end is ____

Answer 9

Pulse duration

Question 10

What happens to the speed of sound in a medium when the bulk modulus of the medium increases?

Answer 10

Faster

Question 11

If a wave’s amp is doubled, what happens to the power?

Answer 11

Quadrupled

Question 12

Power of sound has units of ?

Answer 12

watts

Question 13

The duty factor for continuous wave US is:

10.0

1%

1. 0
2. 0%

Answer 13

1.

Question 14

What are the units of intensity?

Answer 14

Watts/ cm²

Question 15

What happens to the speed of soundi n a medium when the bulk modulus of the medium decreases?

Answer 15

Slower

Question 16

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

Answer 16

10 cm

Question 17

The rayl is the unit of

Answer 17

Impedance

Question 18

Impedance is the ____ of ____ and ___

Answer 18

Product, propagation speed, density

Question 19

Attenuation’s three components

Answer 19

Scattering, reflection, absorption

Question 20

As the impedances of two media become vastly different the

Reflection increases

transmission increases

refraction increases

absorption increases

Answer 20

Reflection increases

Question 21

The angle between an ultrasound pulse and the boundary between two media is 90 degrees. What is this called?

Answer 21

Orthogonal incidence

Question 22

Refraction only occurs if:

Answer 22

There is an oblique incidence (other than 90 degrees) and different propagation speeds

Question 23

With normal incidence, what factors affect refraction of ultrasound?

Propagation speeds

frequencies

attenuation coefficient

none

Answer 23

None

Question 24

With right angle incidence, reflections are always generated at a boundary if the propagation speeds of the media are different.

T or F

Answer 24

False

Question 25

\_\_\_ is a redirection of ultrasound in many directions as a result of a rough boundary between two media

Answer 25

Scattering

Question 26

Snell's lay describes physics of \_\_\_

Answer 26

Refraction

Question 27

The sonographer cannot change, directly or indirectly, the duty factor of an ultrasound machine T or F

Answer 27

false

Question 28

What has the greatest amound of attenuation? Bone fat water muscle

Answer 28

bone

Question 29

Which of these factors has the greatest influence on PRP (pulse repetition period?) Display depth PZT thickness Impedance of medium Dynamic Range

Answer 29

Display depth

Question 30

The region from the transducer to the minimum beam cross sectional area is the:

Answer 30

Fresnel zone (near zone)

Question 31

Which of the following has a propagation speed closest to soft tissue? Muscle fat bone air

Answer 31

Muscle

Question 32

What is the location of the minimum cross sectional area of the US beam called?

Answer 32

Focus

Question 33

The dB is defined as the ___ of two intensities

Answer 33

Ration

Question 34

What is propagation speed determined by?

Answer 34

Density and Stiffness

Question 35

What can be a unit of Amp.? cm Hz msec watts

Answer 35

cm

Question 36

Traveling through the same medium, if the frequency is doubled, the wavelength is :

Answer 36

Halved

Question 37

Traveling through the same medium, if the frequency is doubled, the propagation speed is

Answer 37

unchanged

Question 38

Which of the following is proportional to the square of the amp? period attenuation power frequency speed

Answer 38

Power

Question 39

What is the actual time that an US machine is creating a pulse? Duty factor period pulse period pulse duration \

Answer 39

Pulse duration

Question 40

The angle of incidence of an ultrasound beam is perpendicular to an interface. The two media have the same propagation speeds. What process cannot occur? refraction refleciton transmission attenuation

Answer 40

Refraction

Question 41

The production of a voltage from deformation is called

Answer 41

Piezoelectricity

Question 42

If we increase the frequency, the near zone length is: Increased decreased unchanged

Answer 42

increased

Question 43

If we increase the transducer diameter, the beam diameter in the far zone is Increased decreased unchanged

Answer 43

Increased

Question 44

If we increase the transducer diameter, the beam diameter in the far zone is: increased decreased unchanged

Answer 44

Increased

Question 45

At the focus, the beam diameter is ___ the transducer diameter

Answer 45

Half

Question 46

Another name for Fresnel zone

Answer 46

Near zone

Question 47

Huygen's Principle is based on refraction constructive indices transverse waves interference

Answer 47

interference

Question 48

Descriptions of the shape of a sound wave created by a tiny fragment of PZT

Answer 48

spherical, huygen's wavelet, V shaped

Question 49

What are the effects of damping material?

Answer 49

decreased sensitivity, wide bandwidth, low quality factor

Question 50

Another name for backing material

Answer 50

Damping material

Question 51

How thick is the active element of a 3 MHz pulsed wave transducer? 1. 54 0. 51 half the wavelength of the sound wave in PZT One quarter the wavelength of sound in the matching layer

Answer 51

Half the wavelength of the sound wave in PZT

Question 52

What are the needed conditions for refraction to occur at the boundary between two media?

Answer 52

Different propagtion speed and oblique incidence

Question 53

What remains when the reflected intensity is subtracted from the incident intensity? 1.0 incident intensity transmitted intensity coefficient transmitted intensity

Answer 53

transmitted intensity

Question 54

What is the equation for incident (starting) intensity?

Answer 54

reflected intensity + transmitted intensity

Question 55

What are the units of an incident intensity of a sound wave?

Answer 55

Watts/ cm²

Question 56

What is the amound of attenuation per centrimeter that a sound wave undergoes called?

Answer 56

Attenuation coefficient

Question 57

Which on cannot be a unit of frequency? per day cycles/sec Hz Hertz cycles

Answer 57

Cycles

Question 58

What determines initial amp of US wave

Answer 58

transducer

Question 59

The speed of sound through bone is ___ soft tissue

Answer 59

higher than

Question 60

Units of pulse duration

Answer 60

units of time

Question 61

When reflection occurs with oblique incidence, the angle of reflection equals the angle of incidence. This is known as Snell's law T or F

Answer 61

False

Question 62

What occurs when piezoelectric materials change shape when a voltage is applied to them?

Answer 62

reverse piezoelectric effect

Question 63

The active element is ____ the wavelength

Answer 63

half

Question 64

A shorter pulse has a ___ Q factor

Answer 64

lower

Question 65

Compared to imaging transducers, non-imaging transducers have a _______ sensitivity.

Answer 65

Increased

Question 66

Pulse length is ____ related to pulse duration

Answer 66

directly

Question 67

Q factor is ___ related to bandwidth

Answer 67

inversely

Question 68

The spactial pulse length \_\_\_\_ determines penetration depth generally decreases with frequency related to amp related to medium

Answer 68

generally decreases with frequency

Question 69

the fraction of time the pulsed transducer is on is the \_\_\_\_

Answer 69

Duty Factor

Question 70

The matching layer is ___ the wavelength thick

Answer 70

1/4

Question 71

What is the same meaning as transducer diameter

Answer 71

aperture