C5: Huygen's Principle and Wave interference

Question 1

what is a sine wave

Answer 1

a symmetrical wave that describes the movement of something over time

Question 2

how is an US wave created?

Answer 2

its created by many individual waves that come from their own source and combine to form a wavefront

Question 3

what are the point sources of individual wavelets called

Answer 3

huygens sources

Question 4

what is the name for the waves that are emitted from the huygen sources

Answer 4

huygen wavelets

Question 5

what does the rate of divergence of a huygen wavelet depend on

Answer 5

the size of the source

Question 6

define divergence

Answer 6

the spreading of the sound beam as it travels

Question 7

how are the rate of divergence and the size of the source related

Answer 7

smaller source = larger divergence

inversely

Question 8

define diffraction

Answer 8

diffraction occurs after a beam with planar wavefronts pass through a small aperture (see picture)

Question 9

what is huygens principle

Answer 9

each point source creates its own sound wave or beam… these multiple wavelets from different sources join together to form a wavefront

Question 10

when is it important to consider huygens principle

Answer 10

when designing probes… specifically for resolution and sensitivity

Question 11

what is interference, when does it occur

Answer 11

it occurs when 2 or more waves interact…

it is the adding of the motion of one wave to another

Question 12

2 types of interference

Answer 12

constructive

destructive

Question 13

what 2 wave parameters does interference effect

Answer 13

uniformity and amplification

Question 14

describe constructive interference

Answer 14

the interference of 2 wave that are in-phase… results in an increase in amplitude and intensity

Question 15

describe destructive interference

Answer 15

the interference of 2 wave that are out of-phase… results in a decrease in amplitude and intensity, or the waves may cancel each other out

Question 16

what is a beat frequency

Answer 16

occurs when 2 waves are neither completely in phase, nor completely out of phase

Question 17

how are beat frequency and doppler related

Answer 17

beat frequency is what allows us to detect US doppler signals

Question 18

can changes in intensity effect the sensitivity of the beam

Answer 18

yes

Question 19

which phenomenon is responsible for giving the US beam its natural shape and natural area of focus

Answer 19

interference

Question 20

what are standing waves

Answer 20

occur when 2 waves propagate in the same medium but in opposite directions… when you add these 2 waves together, you will have some points where the amplitude in zero and others where the amplitude is doubled

Question 21

what are the points of minimum fluctuation called in standing waves

do they have high or low pressure

Answer 21

nodes

they have low pressure

Question 22

what are the points of maximum fluctuation called in standing waves

do they have high or low pressure

Answer 22

anti-nodes

they have high pressure

Question 23

what colour will the areas of nodes and anti-nodes be

Answer 23

nodes : black (low intensity)

anti-nodes: bright (high intensity)

Question 24

how do you limit divergence

Answer 24

fire a groups of elements to create a larger wavefront… larger = less divergence