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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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