# Shared Flashcard Set

## Details

Ultrasound Physics
Ch.1-3 Units, Measurements, sound and sound wave
74
Physics
01/17/2021

Term
 Sound waves are
Definition
 Longitudinal and Mechanical waves
Term
 Wavelength is a measure of
Definition
 Distance
Term
 Which is not an acoustic variable? a. Density b. Distance c. Intensity d. Pressure
Definition
 c. Intensity
Term
 Lower frequency waves create higher image quality and better details.
Definition
 False
Term
 Frequency is
Definition
 the # of cycles per second the reciprocal of period inversely related to period
Term
 Waves transfer ___ from one location to another.
Definition
 Energy
Term
 Definition of Period
Definition
 The time for one complete cycle to occur.
Term
 The maximum cyclical change in a quantity is known as
Definition
 Amplitude
Term
 Density is defined as
Definition
 Mass per unit of volume
Term
 Two waves arrive at a location at the same time. What event takes place?
Definition
 Interference
Term
 When you change the fundamental frequency, what changes?
Definition
 The # of cycles per second
Term
 Frequency of a sound waves is determined by
Definition
 The source
Term
 As the frequency of an acoustic variable increases, the wavelength__
Definition
 Decreases
Term
 Terms that can be used to describe the strength of a sound beam are__
Definition
 Amplitude and Intensity
Term
 As the sound wave travels through soft tissue, what happens to the frequency?
Definition
 It is not affected
Term
 Amplitude is measured in__
Definition
 Decibels
Term
 The units label used for power is
Definition
 Watts
Term
 Intensity and power are related to amplitude by
Definition
 Proportional to amplitude squared
Term
 If the power of a wave is halved, the intensity is reduced to 1/4 its value.
Definition
 False
Term
 The formula for intensity is
Definition
 Intensity = Power (watts) ÷ Area (cm2)
Term
 Wavelength is equal to propagation speed__
Definition
 Divided by frequency
Term
 Intensity can be changed by the sonographer.
Definition
 True
Term
 Intensity of ultrasound is measured in__
Definition
 Watts/cm2
Term
 As the wave propagates through the tissue, the amplitude__
Definition
 Decreases
Term
 Wavelength is determined by
Definition
 Source and medium
Term
 Wavelength = propagation speed ÷ by__
Definition
 Frequency
Term
 Image quality is affected by wavelength?
Definition
 True
Term
 If frequency increases, wavelength__
Definition
 Decreases
Term
 Shorter wavelengths create higher quality images with better detail.
Definition
 True
Term
 The # of wavelengths passing a given point in a single second is called__
Definition
 Frequency
Term
 Propagation speed = ____ × wavelength.
Definition
 Frequency
Term
 Propagation speed does not change as frequency increases.
Definition
 True
Term
 If both propagation speed and frequency double, the wavelength will
Definition
 Remain the same
Term
 If stiffness increases, propagation speed__
Definition
 Increases
Term
 U/S travels slowest through__
Definition
 Lungs
Term
 Stiffness of a medium   is the opposite of compressibility/elasticity
Definition
 True
Term
 What term is the reciprocal of Mega?
Definition
 Micro
Term
 Directly related means
Definition
 when one item increases or decreases, the second item responds to the same direction
Term
 Inversely related means
Definition
 Items are related so that the change in one creates an opposite change in the other
Term
 What is not a measurement of area?
Definition
 Cubic meters (volume)
Term
 What is the reciprocal of 5?
Definition
 1/5
Term
 When the elasticity of a medium is high, the___ is high.
Definition
 Compressibility
Term
 What creates the fastest speed of sound?
Definition
 Low density, high stiffness
Term
 The propagation speed used for soft tissue is __
Definition
 An average based on the usual %'s of each type of tissue
Term
 The term bulk modulus is related to which quality?
Definition
 Stiffness
Term
 The ultrasound wave travels faster than the audible wave.
Definition
 False
Term
 What can cause increased propagation speed?
Definition
 Increased stiffness
Term
 The propagation speed of continuous wave ultrasound is faster than pulsed wave ultrasound.
Definition
 False
Term
 Place (liquid, gas, solid) in order of slowest to fastest propagation speed.
Definition
 Gas, Liquid, Solid
Term
 Two quantities are directly proportional if an increase in one quality leads to a/an___ in the other.
Definition
 Increase
Term
 A reciprocal relationship means
Definition
 The items are inversely related. When the reciprocals are multiplied, result is 1. When 1 item increases or decreases, other item does the opposite.
Term
 A measurement of 40mm can also be expressed as __
Definition
 4.0cm
Term
 If the direction of particle motion in a wave is perpendicular to the direction of propagation of the wave, the wave is__
Definition
 Transverse
Term
 The frequency that is closests to the lower limit of ultrasound is __
Definition
 25,000Hz
Term
 The unit measurement for wave frequency is a measurement of __
Definition
 Number
Term
 The frequency of a transducer is 25,000,000 cycles per second. Can be written as__
Definition
 25MHz
Term
 What units are used to report the pressure of a sound beam?
Definition
 Pounds/sq in Pascals (Pa)
Term
 Wavelength depends on which two factors?
Definition
 Frequency and propagation speed
Term
 Constructive interference has the effect of __ the amplitude of a wave.
Definition
 Increasing
Term
 The interaction of echoes that causes reinforcement rather than cancellation is known as__
Definition
 Constructive interference
Term
 If the frequency of an U/S wave is doubled, what happens to the period.
Definition
 Halves
Term
 If frequency is 1MHz, what is the period?
Definition
 1microsec
Term
 If the power of a wave is halved, the intensity is __.
Definition
 Halved
Term
 The following are acoustic parameters except a. pressure b. period      c. propagation speed  d. frequency
Definition
 a. Pressure
Term
 As sound propagations through soft tissue, the amplitude__
Definition
 Decreases proportional to distance
Term
 If the power is doubled, but the intensity remained the same, what happened to the beam area?
Definition
 Doubled
Term
 If the power is doubled, but the intensity remained the same, what happened to the beam area?
Definition
 Doubled
Term
 If the power in a beam is 1 watt and the area is 5cm2, the beam's intensity is __
Definition
 0.2W/cm2
Term
 If the amplitude of a wave is increased by a factor of 3, the power
Definition
 Increased 9 times
Term
 If the amplitude is doubled, the intensity is
Definition
 Increased four times
Term
 If beam area is reduced by half and the power stays the same, intensity__
Definition
 Doubles
Term
 The normal range of intensities used in Doppler ultrasound is __
Definition
 0.2 - 400W/cm2
Term
 What determines the initial amplitude of a sound beam?
Definition
 The transducer
Term
 Which parameter of sound is determined ONLY by the medium?
Definition
 Propagation speed
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