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ultrasound physics.
chapter 3
| Question | Answer |
|---|---|
| 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