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ultrasound physics.

chapter 3

QuestionAnswer
If two waves exist at the same location and combine, this is known as? interference
The speed of sound in soft tissue is? 1540m/sec
Two waves arrive at the same location and interfere with each other. The resultant wave is larger than the original wave. What has occurred? constructive interference
Two waves arrive at the same location and interfere. The resultant wave is smaller than the original wave. What has occurred in this instance? destructive interference
Which of the following transducers would have the greatest depth of penetration? A) 2.5 MHz B) 3.5 MHz C) 5 MHz D) 7.5 MHz a. 2.5MHz
What is the range of periods commonly found in waves produced by ultrasound systems? 0.1-0.5 microseconds
What determines the period of an ultrasound wave? the transducer
How are period and frequency related? inversely (reciprocals)
What is the range of frequencies emitted by transducers used in diagnostic ultrasound? 2MHz-10MHz
What is the characteristic of acoustic waves with frequencies less than 20Hz? humans cant hear them
What determines the initial amplitude of a sound wave? transducers
Mathematically, when a number is squared, the number is multiplied by? itself
As sound travels through the body, what happens to the intensity of the wave? decreases
The intensity of an ultrasound beam is defined as the ______________ in the beam _________ by the _________ of the beam? power, divided, area
What is the wavelength of 2 MHz sound in soft tissue? 0.77mm
If the area of the beam increases, what happens to the intensity? it decreases
What units are used for intensity? watts per cm squared
Which of the following can the sonographer change? (more than one may apply) A) power B) initial amplitude C) initial intensity D) propagation speed a) power, b)initial amplitude, c)initial intensity
If power is doubled, what happens to intensity? it doubles
If amplitude is doubled, what happens to intensity? it quadruples (times 4)
Wavelength is determined by: the source and the medium
What unit of measure is used for wavelength? mm
If the tissue does not change but the frequency of the transducer increases, what happens to the wavelength? it decreases
What factors determine the propagation speed of sound? (more than one may apply) A) density B) composite C) distance traveled D) stiffness a) density, D)stiffness
Sound travels fastest through tissue that is: less dense but more stiff
The amplitude is measured from: the middle value to the minimum value or the middle value to the maximum value
What is period? the time it takes a wave to vibrate a single cycle, or the time from the start of a cycle to the start of the next cycle
What is frequency? the number of cycles that occur in 1 second
why is frequency important in ultrasound? it affects penetration and image quality.
How are power and intensity related? proportional
How are power and amplitude related? power is proportional to the waves amplitude squared.
What is stiffness and how does it effect the speed of sound? the ability of an object to resist compression; as stiffness increases- speed increases (directly related)
What is density and how does it effect the speed of sound? it describes the relative weight of a material; as density increases- speed decreases (inversely related)
what is propagation speed and how is it determined? the distance that a sound beam travels through a medium in one second; by the medium through which the sound is traveling
How are frequency and wavelength related? inversely related
Created by: AshleyLemieux
 

 



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