Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CORE EXAM > Physics 1 Module 5 & 6 > Flashcards

Physics 1 Module 5 & 6 Flashcards

1
Q

The ultrasound beam is created by many waves each emitted by their own source. What is this source called?

A

Huygens’ sources

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the waves called that are emitted from each Huygens’ source?

A

Huygens’ wavelets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

When two waves that are in phase interact and results in increased amplitude and intensity

A

Constructive interference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

When two out of phase waves interfere and results in decreased amplitude and intensity or they may cancel each other out.

A

Destructive interference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

When two waves are neither completely in phase or out of phase

A

Beat frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Two waves propagating in the same medium but in opposite directions, resulting in ares of nodes (low pressure) and anti-nodes (high pressure)

A

Standing waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

1 bel = ____ decibels?

A

10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

A 3 dB drop results in ____ the original intensity?

A

1/2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

A 10 dB drop results in ____ the original intensity?

A

0.1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The amount of attenuation that occurs with each one centimetre travelled

A

Attenuation coefficient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the attenuation coefficient in soft tissue?

A

0.5 dB of attenuation occurs for every one centimetre travelled per 1 MHz therefore,
Attenuation coefficient = 1/2frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the total attenuation equation?

A

TAtt = Att. Coefficient x path length (cm)

In soft tissue:
TAtt = 1/2f x path length (cm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

The distance sound must travel to reduce the intensity to half its original value

A

Half-value layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What 3 factors affect attenuation?

A
  1. Nature of the tissue (necrotic, fluid, etc)
  2. Frequency of the ultrasound
  3. Depth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

The five kinds of attenuation

A
  1. Absorption
  2. Reflection
  3. Refraction
  4. Scatter
  5. Wave-front divergence
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Conversion of sound energy to heat & accounts for around 80% of attenuation

A

Absorption

17
Q

What factors affect absorption?

A
  1. Viscosity (more viscosity = more friction = more absorption)
  2. Relaxation time (higher time = more energy required to reverse direction = more heat)
  3. Frequency (higher frequency = less time for molecules to relax = more absorption)
18
Q

A large surface greater than one wavelength in diameter

A

Specular reflector

19
Q

Why would a reflection of sound not make it back to the probe?

A

Non-perpendicular angle of incidence

20
Q

What is acoustic impedance?

A

Z = density(p) x velocity(c)

21
Q

The larger the difference in Z values, the ______ the reflection

A

Bigger

22
Q

Why do Z values differ within the tissues in the body?

A

Because there are differences in density and stiffness

23
Q

What is an example of a tissue with a very high Z value and one with a very small Z value?

A

Bone is very high

Air is very small

24
Q

Is it possible for 2 tissues to have different sound velocities but have the same Z value?

A

Yes

25
Q

What happens to sound when the velocities differ across the interface and the angle of incidence is non-perpendicular?

A

Refraction

26
Q

What happens if the velocities across the interface are equal?

A

No refraction will occur

27
Q

What happens when the velocity of the first medium is greater than the second?

A

Sound will bend towards the normal (towards y axis)

28
Q

What happens if the velocity of the first medium is less than the second?

A

The sound will refract away from the normal (towards x axis)

29
Q

How does refraction relate to Z values?

A

It doesn’t

30
Q

Sound interacting with interfaces smaller than a wavelength and that are rough & is responsible for the internal texture of organs

A

Scatter

31
Q

Type of scatter when sound is directed back to its origin

A

Backscatter

32
Q

Type of scatter that happens when sound interacts with RBCs

A

Rayleigh scatter

33
Q

Why does the intensity of the beam weaken as it diverges?

A

Due to the relationship between intensity and area (as area increases, intensity decreases), so as the beam spreads apart, it gets weaker

34
Q

The fixed points of amplitude as the result of a standing wave

A

Nodes

35
Q

Point of maximum fluctuation or amplitude as the result of a standing wave

A

Anti-nodes

36
Q

Waves spread out as a result of passing through a narrow aperture

A

Diffraction

CORE EXAM (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions