Sound Beams Flashcards by Kayla Langworthy | Brainscape

Q

What is the region from the transducer to the smallest cross-sectional area of a sound beam called?

a. focus
b. half-value thickness
c. near zone
d. Fraunhofer zone

A

c. near zone

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Q

The area that starts at the beam’s smallest diameter and extends deeper is:

a. the distant zone
b. the Fresnel zone
c. the Fraunhofer zone
d. the depth of penetration

A

c. the Fraunhofer zone

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Q

Which of these terms have the same meaning.

1) far zone
2) near zone
3) Fresnel zone
4) focal zone
5) Fraunhofer zone
6) lateral zone

a. 1 and 2, 3 and 4
b. 1 and 4, 2 and 3
c. 4 and 6, 5 and 1
d. 2 and 3, 5 and 1

A

d. 2 and 3, 5 and 1

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Q

What is the point or location where a beam reaches its smallest dimension?

a. near zone
b. focus
c. penetration depth
d. focal zone

A

b. focus

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Q

All of the following are true of the focus except:

a. it is at the end of the near zone
b. it is at the beginning of the Fraunhofer zone
c. it has the highest spatial peak intensity
d. it is at the start of the Fresnel zone

A

d. it is at the start of the Fresnel zone

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Q

A PZT crystal in the shape of a disc produces a continuous ultrasound wave. The beam is unfocused.

True or False?

The near zone is the only region where the diameter of the sound beam is smaller than the transducer’s.

A

False

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Q

A PZT crystal in the shape of a disc produces a continuous ultrasound wave. The beam is unfocused.

True or False?

The far zone is the only region where the beam diameter exceeds the transducer diameter.

A

True

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Q

A PZT crystal in the shape of a disc produces a continuous ultrasound wave. The beam is unfocused.

True or False?

If the diameter of a sound beam is 8 mm at a depth equal to twice the near zone length, then the PZT crystal has a diameter of 16 mm.

A

False

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Q

A PZT crystal in the shape of a disc produces a continuous ultrasound wave. The beam is unfocused.

True or False?

If the diameter of the acoustic beam produced by a crystal is 8 mm at a depth of twice the near zone length, then the PZT crystal has a diameter of 8 mm.

A

True

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Q

A PZT crystal in the shape of a disc produces a continuous ultrasound wave. The beam is unfocused.

True or False?

The near zone is the only region where the diameter of the sound beam decreases as depth increases.

A

True

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Q

A PZT crystal in the shape of a disc produces a continuous ultrasound wave. The beam is unfocused.

True or False?

If the narrowest diameter of a sound beam is at a depth of 8 cm, then the PZT crystal’s diameter is 16 cm.

A

False

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Q

A PZT crystal in the shape of a disc produces a continuous ultrasound wave. The beam is unfocused.

True or False?

The higher the frequency of the acoustic wave, the shorter the length of the near zone.

A

False

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Q

A PZT crystal in the shape of a disc produces a continuous ultrasound wave. The beam is unfocused.

True or False?

The greater the diameter of a transducer’s piezoelectric crystal, the longer the near zone length is.

A

True

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Q

A PZT crystal in the shape of a disc produces a continuous ultrasound wave. The beam is unfocused.

True or False?

The thicker a continuous wave transducer’s piezoelectric crystal, the longer the near zone length is

A

False

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Q

For a disc-shaped PZT crystal producing continuous sound, which design will create a beam with the shallowest focus?

a. large diameter, low frequency
b. large diameter, high frequency
c. small diameter, low frequency
d. small diameter, high frequency

A

c. small diameter, low frequency

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Q

For a disc-shaped PZT crystal producing continuous sound, which design will create a beam with the deepest focus?

a. large diameter, low frequency
b. large diameter, high frequency
c. small diameter, low frequency
d. small diameter, high frequency

A

b. large diameter, high frequency

Q

Two ultrasound systems are identical except for the diameter of the transducer’s piezoelectric crystal. Which system has the deepest focus?

a. the system with the smaller diameter crystal
b. the one with the larger diameter crystal
c. their foci will be at the same depth

A

b. the one with the larger diameter crystal

Q

Two systems are identical except for the frequency of the emitted pulse. Which system will have the deeper focus?

a. the lower frequency system
b. the higher frequency system
c. both foci will be at the same depth

A

b. the higher frequency system

Q

As sound travels deeply into the far zone, the beam diverges, or spreads out. Which of the following will result in a minimum beam divergence deep in the far zone?

a. small diameter, high frequency
b. high frequency, large diameter
c. large diameter, low frequency
d. low frequency, small diameter

A

b. high frequency, large diameter

Q

As sound travels deeply into the far zone, the beam diverges, or spreads out. Which will result in the greatest beam divergence deep in the far zone?

a. small diameter, high frequency
b. high frequency, large diameter
c. large diameter, low frequency
d. low frequency, small diameter

A

d. low frequency, small diameter

Q

Two ultrasound systems are identical except for the pulse repetition period (PRP) of the emitted pulse. Which system will have the deeper focus?

a. the system with the lower PRP
b. the system with the higher PRP
c. their foci will be at the same depth

A

c. their foci will be at the same depth

Q

All of the following terms describe the shape of a sound wave created by a tiny fragment of PZT except:

a. spherical
b. Huygen’s wavelet
c. V-shaped
d. hourglass shaped

A

d. hourglass shaped

Q

Which of the following explains the difference in sound beam shape created by a disc-shaped crystal from that of a small chip of PZT?

a. Huygen’s Principle
b. Snell’s Law
c. Bernoulli’s Law
d. Murphy’s Law

A

a. Huygen’s Principle

Q

Huygens’ Principle is based on _____.

a. refraction
b. constructive indices
c. transverse waves
d. interference

A

d. interference