Physics Midterm

Sound Waves and Acoustic Variables/Parameters

100

- What type of wave is a electromagnetic source?

- What are the 3 acoustic variables?

1.  Transverse / perpendicular 

Acoustic variables 

    1. Pressure 

    2. Density 

    3. Particle vibration (Distance) 

200

- What are 2 characteristics of constructive interference 

- What are 2 characteristic of destructive interference 

   1. In phase 

   2. Greater amplitude 

   1. Out of phase 

   2. Lesser amplitude

300

- Relationship of stiffness and speed ?

- Relationship of density and speed ?

 directly; inversely 

400

- What are 2 things that frequency effects in ultrasound

resolution and penetration 

500

- speed tissue types

Lowest ? 

Average? 

Highest ?

lowest = lung 

average = soft tissue 

highest = bone 

Intensity and Pulsed Ultrasound

100

   - The beam area is determined by ?

   - relationship of power and intensity ?

   - relationship of area and intensity ?

- transducer 

- directly

- inversely  

200

- two characteristics for long pulses 

- two characteristic for short pulses

    1. many cycles 

    2. cycles with longer wavelength 

    1. Fewer cycles 

    2. Cycles with shorter wavelength

300

- two types of spatial intensities ?

-  three types of temporal intensities ?

 spatial peak and spatial average 

 temporal peak, temporal average, pulse average

400

- What is PRF and PRP ?

- How many cycles in every pulse ( usually) ultrasound? 

- How many cycles are in every pulse in doppler? 

- PRF = Number of pulses per second 

- PRP = Time from the beginning on one pulse to the beginning of the next

- 3 to 5 cycles

- 5 to 30 cycles 

500

- What are the 3 things that change with image depth? 

1. PRP 

2. PRF 

3. Duty factor

Attenuation and Logarithms

100

-  logs of 10², 10³, 10⁴, 10⁰ 

2.0, 3.0, 4.0, 1.0 

200

3 db = ?; -3b = ? 

double ; half 

300

- intensity combined measurements

 lowest?

 highest? 

- highest - sptp 

- lowest-  sata 

400

- three things that total attenuation depends on?

- Frequency 

- Distance 

- Tissue that the sound travels through 

500

- 3 attenuation mechanisms?

 

 - Reflection 

 - Absorption 

 - Scattering

Impedance

100

- What is impedance? 

Determines the amount of an incident beam that is reflected back and the amount that is transmitted to the next medium

200

 - Reflection of an ultrasound wave depends on the _______ in acoustic impedance at the boundary between two media?

- formula of impedance?

 - difference 

 - z (impedance) = p (density of medium) x v (sound propagation speed) 

300

- Acute ?  

- Right ?  

- Obtuse ? 

- less than 90 

- at 90 

- greater than 90 

400

what is transmitted intensity? 

what is reflection intensity?

• The intensity that bounces back to the transducer after it strikes boundary

• The intensity that continues forward in the same direction after its strikes the boundary

500

- Range equation formula ?  

- When depth is superficial PRP is ____ ?

- When depth is deep PRP is _____?

- d= ½ (v x t)

- short

- long

Transducers and Sound Beams

100

- what is Piezoelectric effect?

- what is Reverse Piezoelectric effect?

- Creation of voltage when the material is deformed by applied pressure 

- Creation of pressure when a voltage is applied to the material 

200

- Wavelength of Matching layer?

- Thickness of the crystal? 

 

- 1/4 wavelength

- 1/2 wavelength 

300

- what 3 things does Piezocompostites improve ?

bandwidth, sensitivity, and resolution 

400

- The narrowest point of the beam? 

- For a single disc element the focus is equal to?

- focus 

- one half the width of the element or transducer

500

- The distance from the transducer to the focus?

- The zone from the transducer to the focus?

- focal depth

- near zone