Huygens' Principle and Wave Interference Flashcards
what is a sine wave
a wave that is symmetrical and describes the movement of something with time
Huygens’ sources
point sources that create a wave
Huygens’ wavelets
the waves emitted from each source
wavelets diverge from the source and the rate of divergence depends on the ___ of the source (_____= more divergence)
size
smaller
divergence
the spreading of the beam as it travels from the source
the _____ the source of sound, the less divergence there is
larger
diffraction occurs
after a beam with planar wave fronts pass through an aperature
Huygens’ principle
is that each point source creates its own sound wave or beam
multiple _____ from many sources together form a new ____
wavelets
wave front
Huygens’ principle effects probe design why
typically probes have multiple small crystals mounted on transducer face each with a separate source where all sources form a larger beam together
(impacts sensitivity/res)
interference occurs
when 2 or more waves interact
interference is the ____ of the motion from one wave to that of another
adding
interference 2 categories
constructive
destrcutive
constructive interference (occurs/results)
occurs when two waves are “in phase”
contribution of each wave results in an increase in amp/intensity
destructive interference (occurs/results)
occurs when two waves are “out of phase”
contribution of both results in an decrease in amp/intensity or cancel out
when two waves are neither completely in phase nor out of phase a ______ is produced
beat frequency
beat frequency
occurs when two waves are neither completely in phase nor out of phase
changes in intensity can effect the ____ of the beam
sensitivity
what does beat frequency have to do with ultrasound
how doppler signals are detected in ultrasound (send out on F, get a different F back)
interference effects the ____ of the beams intensity and amplification throughout the ______
uniformity
ultrasonic field
interference gives the beam a ____ responsible for the ______ of the beam
shape
natural focusing
beam shape is also important when considering the image ______
resolution
standing waves occur/results
when two waves propagate in the same medium but in opposite directions resulting in some points where amplitude is zero and others where amp is doubled
nodes
points of minimum fluctuation and are points of low pressure (smallest difference in wave amp)
anti-nodes
the points of maximum fluctuation and are points of high pressure (biggest difference in wave amp)
standing waves can give rise to areas of ____ or _____ amplitude
enhanced
decreased
All points on a wave front are sources of secondary waves
Hyugens’ principle
A vibration of a system in which some particular points remain fixed while others between them vibrate with the maximum amplitude
standing wave
Several wavelets traveling together in a medium create a:
wave front
Waves spread out as a result of passing through a narrow aperture
diffraction
A symmetrical representation of the movement of something over time
sine wave
Two or more waves added together where the resultant amplitude is greater than the original
constructive interference
The sound wave emitted from each point source that contribute to the overall wavefront
HUYGENs WAVELETS
When two or more waves interfere and are not completely in or out of phase
beat freqeuncy
Two or more waves added together where the resultant amplitude is less than the original
destructive interference
Individual sources of sound that result in a wavefront when they interfere
Huygens’ sources
The fixed points of amplitude as the result of a standing wave
nodes
What is the result when two waves of equal amplitude, frequency and are 180 degrees out of phase interfere with one another?
total destructive interference
Explain the significance of a standing wave in relation to the potential effects that can be observed on an ultrasound image
the areas of nodes can result in areas of darkness on the screen where areas of antinodes can create areas of brightness
How does Huygens’ Principle apply to transducer construction and design?
Understanding the way that the wavelets from the probe interact allow the ability to alter the shape of the beam for the purpose of steering and focusing. This will impact the sensitivity and resolution of the image.
