Physics Test 1
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Physics Test 1
dorkfork ultrasound sonography waves physics
Test 1, Ultrasound Physics and Instrumentation
Sound is classified as __________ energy.
The general oscillatory movement of the molecules in respone to the interation of ultrasound energy is called _______ _________ _______.
simple harmonic motion
In the medium, one area of increased pressure is called _______.
In a medium, one area of decreased pressure is _________.
rarefaction or decompression
What is the type of wave motion where the molecules oscillate in the same direction as the sound energy travel?
Longitudinal oscillatory motion most frequently occurs in what type of medium?
What is the type of wave motion where the molecules oscillate at 50 degrees relative to the direction of sound energy propagation?
Shear waves most frequently occur in what kind of medium?
What is the definition of a cycle?
One area of compression + one area of rarefaction.
What is the definition of frequency?
Number of cycles per second.
What is the unit of measurement of frequency?
What are the categories within the sound spectrum?
: below 20Hz
: above 20,000Hz
: 2.25MHz & up
What is the definition of period?
The time it takes for one cycle to occur.
What is the definition of wavelength?
The distance that one cycle travels.
What is the definition of amplitude?
maximum pressure variation in a cycle (the strength of the wave) aka the pressure gradiant
What is the definition of power?
Rare that energy is transferred (controlled by the acoustic power control)
What is the equation that demonstrates the relationship between power and intensity?
power = intensity
What is the equation that demonstrates the relationship between power and amplitude?
power = amplitude
What is the equation that demonstrates the relationship between intensity and amplitude?
What are the units of measurement for power, intensity, and amplitude in clinical aplications?
: dB (decibels)
If the amplitude is increased by a factor of 3, the power is increased by a factor of __.
If the power is increased by a factor of 3, the intensity increases by a factor of __.
If the amplitude is increased by a factor of 4, the intensity increases by a factor of __.
If the beam area is reduced to 1/2, the intensity equals __.
Decreasing the intensity to 1/8 of the original intensity = ___ dB.
Decreasing the intensity to 1/4 of the original intensity = __ dB.
Decreasing the intensity to 1/2 of the original intensity = __ dB.
Decreasing the intensity by a factor of 10 = __ dB.
Increasing the intensity by a factor of 10 = ___dB.
Doubling intensity = ___ dB.
Increasing intensity by a factor of 4 = ___ dB.
Increasing intensity by a factor of 8 = ___ dB.
What is the definition of intensity?
Power of sound field divided by beam cross section area.
The propagation speed is slowest in what type of medium?
The propagation speed is fastest in what type of medium?
What is the average propagation speed in soft tissue?
1.54 mm/μs or 1540 m/s
Soft tissue is classified as what type of medium - gas, liquid, or solid?
What is the mathematical relationship between wavelength and frequency?
because c (propagation velosity) is a constant... ALWAYS 1.54mm/μs
What are the primary characteristics of the medium that determine the propagation speed? What is the mathematical relationship?
density and elasticity
c=E/ρ or propagation speed=elasticity/density
If the wavelength is doubled, the frequency will ____.
decrease by 1/2
What is the mathematical relationship between frequency and period?
If the frequency is reduced to 1/2, the period will ____.
increase by 2
What is the mathematical relationship between period and frequency?
propagation velocity = _______ x wavelength
What is the average propagation speed for gasses, liquids and solids?
: 400 m/s
: 1540 m/s
: 4000 m/s
What does the log equation do?
Allows us to convert intensity into dB notation. This provides a standard measurement for intensity on all equipment.
dB= 10 log
What are the clinically relevant metric units?
What is the order of metric units using 1 meter as the base unit.
Intensity is equal to Power divided by the _______.
What are the clinically relevant measurements for frequency, wavelength, and period?
frequency = MHz
wavelength = mm
period = μs
What are the mathematical relationships between frequency and λ, frequency and period?
frequency and wavelength are inversely related
frequency and period are inversely related
What information must be known in order to convert intensity into dB?
two intensity levels f