Huygens’ Principle And Wave Interference Flashcards
What is attenuations?
Weakening of sound as it travels
What is a sine wave?
A symmetric wave that describes the movement of something with time
What are Huygens’ Sources?
The idea that ultrasound beams is actually created by many waves each emitted by their own source. Which is Huygens sources
What are Huygens’ Wavelets?
Waves emitted from each source.
What does changing the size of the sources do for the wavelets?
These wavelets diverge from the source and the rate of divergence depends on as the size of the source
What is divergence?
The spreading of the beam as it travels from the source
If we have a larger source what does that do to the divergence?
The larger the source of sound the less divergence there is
When does diffraction occur?
Occurs after a beam with planar wave fronts pass through a small aperture
What is Huygens’ Principle?
Each point source creates its own sound wave or beam. Basically, multiple wavelets from many sources together form a new wave-front
Why is Huygens’ principle important?
It is important to consider during the designing of probes.
How are typical probes designed?
1.They generally have a array of multiple small elements or crystal mounted on the transducer face.
2. Each crystal is its own separate source and all of the sound sources together create the larger beam
What is interference?
When two or more waves interact
What is sensitivity?
The ability to pick up weak echoes
What is an example of interference?
Adding of the motion from one wave to that of another
What can interference be categorized as?
Constructive or destructive
What is constructive interference?
When two waves are “in phase” and the contribution of each wave results in an increase in amplitude and intensity
What is destructive interference?
When two waves are “out of phase” and the contribution of each wave results in a decrease in amplitude and intensity or they may simply cancel each other out
What is beat frequency?
When two waves are neither completely in phase nor out of phase
How are Doppler signals detected in ultrasound? (What do we use?)
We use beat frequency
Interference effects what?
The uniformity of the beams intensity and amplification throughout the ultrasonic field.
What does changes in intensity do?
Effects the sensitivity of the beam
Interferences also gives what in terms of the beam?
Gives the shape of the beam responsible for the natural focusing of the beam
Why is beam shape important?
Important in terms of considering the image resolution
When do standing waves occur?
When two waves propagate in the same medium but in opposite directions
What are nodes?
Points of minimum fluctuation and are points of low pressure
What are anti nodes?
Points of maximum fluctuation and are points of high pressure
Standing wave can give rise to what?
Areas of enhanced or decreased amplitude
