Physics 1 Test Ch 8, 9

Question 1

Correctly describe an imaging transducer

Answer 1

short duration and length of pulses
use backing material (damping) to limit ringing
low sensitivity
wide bandwidth/broadband
low Q-factor
improved axial resolution
p.119

Question 2

When PZT exceeds the Curie point what happens to it?

Answer 2

When PZT’s temperature exceeds the Curie point, the PZT is depolarized. PZT’s properties are lost forever and the transducer in ruined.
p.121

Question 3

Piezoelectric materials change shape when a voltage is applied to them, what is that process called?

Answer 3

Reverse Piezoelectric Effect

p.113

Question 4

PZT is also known as…

Answer 4

Piezoelectric
Ferroelectric
Lead Zirconate Titanate 
Ceramic
Active Element
Crystal
p.113

Question 5

Which transducer component reduces the ringing of the pulse?

Answer 5

Backing Material, also known as damping element

p.115

Question 6

Mathematically, the Q-factor is the main frequency divided by what?

Answer 6

Q-factor = main frequency ÷ bandwidth

p.119

Question 7

Imaging transducers can also be referred to as…

Answer 7

MAYBE “ pulsed wave transducer” ??????

Question 8

Which crystals will produce sound with a lower frequency?

Answer 8

thicker PZT crystals and PZT with lower speeds

p.125

Question 9

The acoustic impedance of the matching layer is approximately the same impedance as what?

Answer 9

In between that of the active element and the skin Pg 116 The impedance of the matching layer is about the same as the gel we use in US.

Question 10

Which of the following determines the frequency of sound created by a pulsed wave transducer?

Answer 10

speed of sound in the PZT
thickness of the PZT
p.123

Question 11

Which of the following determines the focal length of the sound beam?

Answer 11

transducer diameter
frequency of sound
p.135

Question 12

Which of the following determines the spread of the sound beam in the far field?

Answer 12

transducer diameter
frequency of sound
p.139

Question 13

Which of the following transducers has the most shallow focus? (gives us frequency of transducer and crystal diameter)

Answer 13

Transducer with smallest diameter and lowest frequency.

p.138

Question 14

Which of the following transducers has the shallowest focus? (frequency and large or small crystal)

Answer 14

lower frequency and small diameter crystal

p.136

Question 15

Which of the following transducers has the deepest focus?

Answer 15

Transducer largest diameter and highest frequency.

p.138

Question 16

Which transducer has the least divergence in the far field?

Answer 16

Transducer with the largest diameter and higher frequency.

p.140

Question 17

The frequency of the transducer does not change, if the diameter of the new PZT increases, what happens to the beam diameter in the far zone?

Answer 17

decreases

p.143

Question 18

The frequency of the transducer does not change, if the diameter of the new PZT increases, what happens to the near zone length?

Answer 18

increases

p.143

Question 19

The frequency of the transducer does not change, if the diameter of the new PZT increases, what happens to the wavelength?

Answer 19

no change

p.143

Question 20

Which of the following has the deepest location? (at the end of the near zone, at the end of the far zone, end of focal zone, Fresnel)

Answer 20

The far zone (Fraunhofer zone)

p.144)

Question 21

What is the shape of the sound beam created by tiny PZT crystals?

Answer 21

V-shaped

p.144

Question 22

Beam diameter is equal to the transducer diameter at what location?

Answer 22

at 2 near zone lengths

p.132

Question 23

Damping material in the transducer improves the systems _____ resolution.

Answer 23

longitudinal
p.126
Axial
p. 115

(Same thing, different terms)

Question 24

If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6MHz, then the operating frequency of the transducer is how many MHZ?

Answer 24

frequency is not determined by electrical signal in pulsed wave transducers
p.126

Question 25

If the frequency of the electrical excitation voltage of a continuous wave transducer is 6MHz, then the operating frequency of the transducer is how many MHz?

Answer 25

6MHz (freq of voltage = operating freq in cont. waves)

p.127

Question 26

Impedance of a transducer’s active element is 1,900,000 rayls, and the impedance of the skin is 1,400,000 rayls. What is an acceptable impedance of the matching layer?

Answer 26

1,726,000 rayls (or the number between the 2 impedances)

p.127

Question 27

Which transducer component has cork and rubber on it?

Answer 27

acoustic insulator

p.115

Question 28

Which transducer component increases efficiency of sound energy between the active element and the body?

Answer 28

matching layer

p.115

Question 29

Frequency and near zone length are related in what way? (inversely, directly, etc…)

Answer 29

Directly

p.136

Question 30

Two transducers have the same diameter, but different frequencies, which beam will have a shallower focus?

Answer 30

lower frequency probe

p.136

Question 31

We are given frequencies and diameters, which has the least divergence?

Answer 31

larger diameter, higher frequency probe

p.140

Question 32

We are given frequencies and diameters, which has the most divergence?

Answer 32

smaller diameter, lower frequency probe

p.140

Question 33

Which of the following determines the frequency of sound created by a pulsed wave transducer?

Answer 33

1. Speed of sound in the PZT
2. Thickness of the PZT
   p. 123

Question 34

Which factors determine the spread of the sound beam in the far field?

Answer 34

transducer diameter
frequency of sound
p.139