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Physics Unit 1 test

QuestionAnswer
A wave is a traveling variation in quantities called wave _________? Variables
Sound is a traveling vaiation in quantites called _________ variables. Acoustic
Ultrasoud is sound with a frequency greater than __________ Hz. 20,000
Acoustic variables include _________, __________, and particle vibration. pressure, density
Which of the folling is not an acoustic variable? A. Pressure B. Propagation Speed C. Density D. Particle Motion B. Propagation Speed
Frequency is the number of ________ an acoustic variable goes through in a second. Cycles
The unit of frequency is ________, which is abbreviated ________. hertz, Hz
Period is the ________ that it takes for one cycle to occur. Time
Period DECREASES as _________ INCREASES. Frequency
Wavelength is the length of ________ which one cycle occurs. Space
Popagation speed is teh speed with which a(n) _______ moves through a medium. Wave
Wavelength is equal to ________ _________ divided by _________. Propagation Speed, Frequency
The ________ and ________ of a medium determine propagation speed. Density, Stiffness
Propagation speed INCREASES if ________ is INCREASED. Stiffness
The average propagation speed in soft tissues is ________ m/s or ________ mm/microsecond. 1540, 1.54
Propagation speed is determinded by the ________. Medium
Place the following in order of increasing sound propagation speed: Liquid, Solid, Gas Gas - Liquid - Solid
The wavelength of 7 - MHz ultrasound in soft tissues is ________ mm. .22
Wavelength in soft tissues ________ as frequency INCREASES. INCREASES
It takes ________ microseconds for ultrasound to travel 1.54 cm in soft tissue. 10
Propagation speed in bone is ________ that in soft tissues. Higher than
Sound travels faster in ________. A. Air B. Helium C. Water D. Steel D. Steel (fastest in solids)
Solids have higher propagation speeds than liquids because they have greater ________. Stiffness
Sound travels slowest in ________. Gases
Sound is a ________ ________ wave. Mechanical, Longitudinal or Compressed
If propagation speed is doubled (a different medium) and frequency is held constant, the wavelength is ________. Doubled
If the wavelength is 2mm and frequency is doubled, the wavelength becomes ________ mm. 1
If frequency in soft tissue is doubled, propagation speed is ________. Unchanged (determined by medium)
Waves can carry ________ from one place to another. Information
T or F - If two media have different stiffnesses, the one with the higher stiffness will have the higher propagation speed. True
The second harmonic of 3 MHz is ________ MHz. 6
The odd harmonics of 2 MHz are ________ MHz. 6, 10, 14
The even harmonic of 2 MHz are ________ MHz. 4, 8, 12
Nonlinear propagation means that ________ . Propagation speed depends on pressure and the waveform changes shape as it travels
T or F - If two media have the same propagatio speed but different densities, the one with the higher density will have the higher impedance. True
T or F - If two media have the same density but different propagation speeds, the one with the higher propagation speed will have the higher impedance. True
Impedance is ________ multiplied by ________ ________. Density x Propagation Speed
The abbreviation CW stands for ________. Continous Wave
Pulse Repetition Frequence (PRF) is the number of ________ occuring in 1 second. Pulses
Pulse Repetition ________ is the time from the beginning of one pulse to the beginning of the next. Period
Pulse Repetition Period (PRP) ________ as PRF INCREASES. DECREASES
Pulse duration is the ________ it takes for a pulse to occur. Time
Spatial pulse length (SPL) is the ________ of ________ that a pulse occupies as it travels. Length, Space
________ ________ is the FRACTION of time that pulsed ultrasound is actually on. Duty factor
Pulse duation equals the number of cycles in the pulse multiplied by ________. Period
SPL equals the number of cycles in the pulse multiplied by ________. Wavelength
The duty factor of continuous wave sound is ________. 1 (100%)
If the wavelength is 2mm, the SPL for a three-cycle pulse is ________ mm. 6
The pulse duration in soft tissue for a two-cycle pulse of frequency 5 MHz is ________ microseconds. .4 (Period is .2 ms, soft tissue is irrelevant.)
For a 1-kHz PRF, the pulse repetition period is ________ ms. 1 (1,000 pulses per second)
How many cycles are there in 1 second of continuous wave 5-MHz ultrasound? 5,000,000
How many cycles are there in 1 second of pulsed 5-MHz ultrasound with a duty factor of .01(1%)? 50,000
For pulsed ultrasound, the duty factor is always ________ ________ one. Less than
________ is a typical duty factor for sonography. .1
Amplitude is the maximum ________ that occurs in an acoustic variable. Variation
Intensity is the ________ in a wave divided by ________. Power, Area I = P/A
The unit for intensity is ________. W/cm^2 or mW/cm^2
Intensity is proportional to ________ squared. Amplitude
If power is doubled and area remains unchanged, intensity is ________. Doubled
If area is doubled and power remains unchanged, intensity is ________. Halved
If both power and area are doubled, intensity is ________. Unchanged
If amplitude is doubled, intensity is ________. Quadrupled
Attenuation is teh reduction in ________ and ________ as a wave travels through a MEDIUM. Amplitude, Intensity
Attenuation consists of ________, ________, and ________. Absorbition, Reflection, Scattering.
The Attenuation Coefficient is attenuation per ________ of sound travel. CM (Centimeter)
Attenuation and teh attenuation coefficient are given units of ________ and ________, respectively. dB, dB/cm
For soft tissues, there is approx. ________ dB of attenuation per cm for each MHz of frequency. .5
For soft tissues, the attenuation coefficient at 3 MHz is approx ________. 1.5 dB/cm
the attenuation coefficient in soft tissue ________ as frequency INCREASES. INCREASES
For soft tissue, if frequency is doubled, attenuation is ________. Doubled
If path length is doubled attenuatio is ________. Doubled
If both frequency and path length are doubled, attenuation is ________. Quadrupled
If frequency is doubled and path length is halved, attenuation is ________. Unchanged
Absorption is the conversion of ________ to ________. Sound to Heat
Can absorption be greater than attenuation in a given medium at a given frequency? No
Is attenuation in bone higher or lower than in soft tissue? Higher
The imaging depth (penetration) ________ as frequency INCREASES. DECREASES
When ultrasound encounters a boundary with perpendicular incidence, the ________ of the tissues must be different to produce a reflection (echo). Impedances
With perp incidence, two media ________ and the incident ________ must be known to calculate the reflected intensity. Impedances, Intensity
With perep incidence, two media ________ must be known to calculate the intensity reflection coefficient. Impedances
T or F - If the impedances of the media are equal, there is no reflection. True For perp incidence
With perep incidence, the reflected intensity depends on the ________. Impedance difference and impedance sum
Refraction is a change in ________ of sound when it crosses a boundray. Direction
Refraction is caused by a change in ________ ________ at the boundary. Propagation speed.
Under what tow conditions does refraction NOT occur? Perp incidence & Equal media propagation speeds
Redirection of sound in MANY directions as it encounters a rough media or particle suspensions (hetrogeneous media) is called ________. Scattering
T or F - Backscatter helps make echo reception less dependent on incident angle. True
What mus be known to calculate the distance to a reflector? Travel time and Speed
No reflection wil occur with perpendicular incidence if the media ________ are equal. Impedances
T or F - Scattering occurs at smooth boundaries and within homogenous media. False
The sound that encourtered a boundary btwn 2 media (BB2M) & travels thru onto the next BB2M is ________. Transmission
Portion of sound returned from a media boundary (Echos) is ________. Reflection
Rate at which energy passes through a unit area is ________. Intensity
If power INCREASES, intensity ________. INCREASES
If frequency INCREASES, attenuation coefficient ________. INCREASES
If frequency INCREASES, attenuation ________. INCREASES
2 or more cycles of waves followed by a RESTING TIME describes a ________. Pulse
The unit for Amplitued is ________. Pa (Pascals)
The amount of time fron the BEGINNING to END of a single PULSE is ________. THIS EXCULDES RESTING TIME!!! Pulse duration
Start of one pulse to the start of the next is ________. This INCLUDES LISTENING TIME!!! PRP
The formula for PRP = ________. PRP = 1/PRF Recipricol of PRF
Duty factor compares machine ________ time to the listening or ________ time. Fraction of time the transducer is "ON". On, Off
If PRP INCREASES, Duty Factor ________. DECREASES
Avg. Duty Factor is ________ %. 1-2
If image depth INCREASES, PRF ________. DECREASES
Created by: qtpants7 on 2011-02-21



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