Flashcards in Physics Final Deck (134)
T/F Macro means bigger and micro means smaller
T/F The symbol for millions is mega and millionths is micro
T/F The symbol for hundreds is giga and the symbol for hundredths is hecto
False; hundreds is hecto (h), hundredths is centi (c)
T/F A wave with a frequency of 15,000 MHz is ultrasonic
T/F If the power of a wave is halved, the intensity is reduced to one-fourth its original value
False; intensity is the power of a beam divided by its cross-sectional area. If we halve the power, we will halve the intensity
T/F If the amplitude of a wave is increased to 3 times its original value, the intensity is increased by 6 times
False; Intensity is proportional to the amplitude squared. If we triple the amplitude, we increase the intensity by a factor of nine.
T/F Propagation speed is determined by the medium
T/F Propagation speed increases as frequency increases
False; they are unrelated
T/F We need one intensity to calculate decibels
False; we need two intensities to calculate decibels
T/F As the path length increases, attenuation of US in soft tissue increases
T/F Spatial peak intensity is always lower than the spatial average intensity
False; Spatial peak intensity is always higher than the spatial average intensity
T/F In addition to location within the beam, sound wave intensities also vary over time
T/F SPTA intensity is the most relevant intensity with respect to tissue heating
T/F The duty factor is a unit less number with a value between 0 and 1
T/F There are two different methods to measure and report intensities
False; there are 6 different methods to measure and report intensities
T/F The duty factor for a pulsed ultrasound system is 2%.
False; with anatomic imaging the duty factor is 0.2%
T/F An ultrasound beam has the same intensity at different depths or at different side to side locations within the beam
False; the beam will have different intensities
T/F At a particular depth, the center of a sound beam is more intense than the edges
T/F Temporal peak intensity is maximum in time
How many hertz is 3MHz?
How much bigger is a billion than a million?
What are the units of wavelength?
unit of length, mm or m
What are the units of frequency?
What are the units of intensity?
What are the units of propagation speed?
units: m/s, mm/ μs, or any distance divided by time
What are the units of period?
units of time, microseconds, seconds, hours, or days
Of the following which grouping is determined by the sound source?
Amplitude, power, intensity
If the intensity remains the same while the power is doubled, what happens to the beam area?
A sound beam travels a total of 10cm in 2 seconds. What is the speed of the sound in this medium?