Module 5 : Huygens Principle

Question 1

what is a sine wave

Answer 1

• symmetric wave that describes the movement of something over time

Question 2

does the ultrasound wave create one wave or multiple

Answer 2

• multiple from their own sources

Question 3

what are the point sources called and what are the wavelets called

Answer 3

• Huygens sources

- Huygens wavelets

Question 4

what is divergence

Answer 4

• the spreading of the beam as it travels

Question 5

what controls the rate of divergence

Answer 5

• larger the source of sound the less divergence

Question 6

what is diffraction

Answer 6

• occurs when a beam with planar fronts pass through a small aperture

Question 7

what is Huygens principle

Answer 7

• each point source creates its own sound wave

- multiple wavelets from many sources together from a new wavefront

Question 8

how is Huygens principle used in probe design

Answer 8

typical probes have an array of multiple small elements or crystals mounted on the transducer face

• each crystal is a separate source and all the sound sources together create a mean larger beam
• this impacts resolution and sensitivity

Question 9

what is interference

Answer 9

• occurs when 2 or more waves interact

- adding of the motion one wave to that of another

Question 10

what are the two types of interference

Answer 10

• constructive and destructive

Question 11

what is constructive interference

Answer 11

• when 2 waves or in phase and the contribution of each wave results in an increase in amplitude and intensity

Question 12

what is destructive interference

Answer 12

• when 2 waves are out of phase and the contribution of each wave results in a decrease in amplitude and intensity
• or just cancel each other out

Question 13

what occurs when the waves are not completely in or out of phase

Answer 13

• beat frequency

- doppler uses this

Question 14

what is interference responsible for in regards to the beam

Answer 14

• uniformity of intensity and amplification
• sensitivity
• beam shape

Question 15

what is a standing wave

Answer 15

• occur when two waves propagate in the same medium but different directions
• when you add the waves together some points reach zero and others have doubled amplitude

Question 16

what are the points of minimum fluctuation called in a standing wave

Answer 16

• nodes

Question 17

what are the points of maximum fluctuation called in a standing wave

Answer 17

• antinodes