Huygen's Principle & Attenuation

Question 1

Huygen’s Principle

Answer 1

each point source creates its own wavelet, and from them a collective wavefront forms

Question 2

divergence

Answer 2

the spreading out of a wave as it travels further from the source

Question 3

diffraction

Answer 3

divergence of a wave after passing through a small aperture

Question 4

interference

Answer 4

the combining of waves as they travel

Question 5

constructive interference

Answer 5

sum of the amplitudes in waves that are in phase with one another resulting in a single with larger amplitude

Question 6

destructive interference

Answer 6

sum of the amplitudes in waves that are out of phase with one another resulting in a wave with smaller or fully neutralized amplitude

Question 7

beat frequency

Answer 7

sum of the amplitudes in two waves of similar frequency resulting in a new wave with areas of alternating increased and decreased amplitudes

Question 8

sensitivity

Answer 8

ability to detect weak echoes

Question 9

What type of resolution is affected by divergence?

Answer 9

lateral resolution

Question 10

nodes

Answer 10

points of low pressure/minimum fluctuation on a standing wave

Question 11

antinodes

Answer 11

points of high pressure/maximum fluctuation on a standing wave

Question 12

standing wave

Answer 12

sum of two waves propagating in opposite directions, resulting in a wave oscillating around a fixed axis which has a series of alternating nodes and anti-nodes

Question 13

standing wave envelope

Answer 13

the abstract boundary of the maximum fluctuations of a standing wave as it oscillates around a fixed axis

Question 14

each point source creates its own beam, and collectively a wavefront is created

Answer 14

Huygen’s Principle

Question 15

the spreading out of a wave as it travels further from the source

Answer 15

divergence

Question 16

divergence of a wave after passing through a small aperture

Answer 16

diffraction

Question 17

the combining of waves as they travel

Answer 17

interference

Question 18

sum of the amplitudes in waves that are in phase with one another resulting in a single with larger amplitude

Answer 18

constructive interference

Question 19

sum of the amplitudes in waves that are out of phase with one another resulting in a wave with smaller or fully neutralized amplitude

Answer 19

destructive interference

Question 20

sum of the amplitudes in two waves of similar frequency resulting in a new wave with areas of alternating increased and decreased amplitudes

Answer 20

beat frequency

Question 21

ability to detect weak echoes

Answer 21

sensitivity

Question 22

points of low pressure/minimum fluctuation on a standing wave

Answer 22

nodes

Question 23

points of high pressure/maximum fluctuation on a standing wave

Answer 23

antinodes

Question 24

sum of two waves propagating in opposite directions, resulting in a wave oscillating around a fixed axis which has a series of alternating nodes and anti-nodes

Answer 24

standing wave

Question 25

the abstract boundary of the maximum fluctuations of a standing wave as it oscillates around a fixed axis

Answer 25

standing wave envelope

Question 26

Huygen sources, aka

Answer 26

point sources

Question 27

point sources, aka

Answer 27

Huygen sources

Question 28

Huygen wavelet

Answer 28

single wave emitted from a Huygen source

Question 29

single wave emitted from a Huygen source

Answer 29

Huygen wavelet

Question 30

relationship between size of sound source & rate of divergence

Answer 30

inverse relationship

Question 31

How many decibels are in a Bel?

Answer 31

10 decibels per Bel

Question 32

How many Bels are in a decibel?

Answer 32

1/10 Bels per decibel

Question 33

units of attenuation or gains

Answer 33

decibels

Question 34

units of intensity

Answer 34

mW/cm2

Question 35

attenuation

Answer 35

weakening of a sound beam as it travels

Question 36

weakening of a sound beam as it travels

Answer 36

attenuation

Question 37

dominant factor contributing to attenuation in soft tissues

Answer 37

absorption

Question 38

absorption

Answer 38

conversion of sound energy to heat

Question 39

conversion of sound energy to heat

Answer 39

absorption

Question 40

attenuation coefficient

Answer 40

amount of attenuation that occurs with each centimeter the sound travels

Question 41

amount of attenuation that occurs with each centimeter the sound travels

Answer 41

attenuation coefficient

Question 42

five causes of attenuation

Answer 42

absorption, reflection, refraction, scatter, wave-front divergence

Question 43

absorption, reflection, refraction, scatter, wave-front divergence

Answer 43

causes of attenuation

Question 44

three causes for variance of attenuation

Answer 44

nature of tissue, frequency, depth

Question 45

nature of tissue, frequency, depth

Answer 45

causes for variance of attenuation

Question 46

State the attenuation coefficient in soft tissue

Answer 46

0.5 dB are attenuated in one centimeter for every 1 MHz

Question 47

Is total attenuation expressed as a positive or negative?

Answer 47

positive

Question 48

Is attenuation expressed as a positive or negative?

Answer 48

negative

Question 49

Are gains expressed as a positive or negative?

Answer 49

positive

Question 50

What are the relationships btwn attenuation, frequency and depth?

Answer 50

as attenuation is directly proportional to frequency and inversely proportional to depth

Question 51

half-value layer

Answer 51

the thickness of a medium that causes the sound wave to lose half the intensity of its original value

Question 52

the thickness of a medium that causes the sound wave to lose half the intensity of its original value

Answer 52

half-value layer

Question 53

three factors that influence absorption

Answer 53

frequency, viscosity, relaxation time

Question 54

frequency, viscosity, relaxation time

Answer 54

three factors that influence absorption

Question 55

explain how viscosity influences absorption

Answer 55

more friction btwn the molecules

Question 56

explain how frequency influences absorption

Answer 56

more friction btwn molecules, more often

Question 57

explain how relaxation time influences absorption

Answer 57

it takes more energy to move the molecules in the opposite direction when they are still moving have not yet come to rest