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Physics Unit 1 test
| Question | Answer |
|---|---|
| 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 |
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qtpants7
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