Physics 1 Test Ch 6, 7 Flashcards
How is intensity calculated?
Power/area
What are the units for intensity?
W/cm^2
What are the names for normal incidence?
Perpendicular Orthogonal Right angle Normal Ninety degrees
Any angle other than 90 degrees
Oblique
An acute angle is..
Less than 90 degrees
An obtuse angle is..
Greater than 90 degrees
intensity of sound wave at the instant prior to striking a boundary is called…
Incident intensity
the portion of incident intensity and reflected completly
Reflected intensity
normal incidence is what degree?
90 degrees
portion of incident intensity after striking boundary that continues?
Transmitted intensity
% of ultrasound intensity when sound strikes a boundary?
Intensity Reflection Coefficient (IRC)
% of ultrasound that is allowed to pass through?
Intensity Transmission Coefficient (ITC)
Intensity reflection coefficient and intensity transmission coefficient have what units?
No units
They are percentages
with normal incidence,reflection depends upon different what?
Different impedance
a large reflection will occur in normal incidence if impedance are what?
Substantially different
with greater impedance differences the IRC increases and the amount of reflection?
I found this information online I think…
reflection increases
specular reflections arise when the interface is…
Smooth
The 2 physical principles always apply to oblique incidence
1) Conservation of energy
2) Reflection angle=incident angle
What do we know about oblique incidence?
NOTHING
what is transmission with a bend?
Refraction
With oblique incidence and different propagation speeds what can occur?
Refraction
Snells law describes what in physics?
Refraction
A sound wave strikes a boundary with normal incidence, if impedances are identical, what % of sound is refracted?
0%
Because if impedance is the same there is no reflection
What best describes reflection arising from a rough boundary?
Diffuse reflection/ Backscatter
What processes occur when ultrasound passes through all media?
Attenuation ( scattering, absorption, reflection )
What is the % of time that a system is transmitting a pulse?
Duty factor
*i thought this question was hard to find because it’s from chapter 4
What is the dominant contributor to attenuation?
Absorption
As path length increases attenuation…
Increases
Impedance is a characteristic of …
The medium only
Reflection occurs only if the 2 media have…
Different impedances
As path length increase the attenuation coefficient …
stays the same
IRC
% of intensity that bounces back when sound beam strikes boundary between two media
ITC
% of intensity that passed in the forward direction when the beam strikes an interface between two media
What is the best estimate for attenuation coefficient of sound traveling in soft tissue?
the attenuation coefficient is one half the frequency used in soft tissue. atten. coef.=.5 dB/cm/MHz
2 factors for attenuation…
Path length
Frequency of sound
How is attenuation affected by distance?
Distance and attenuation are directly related-
The farther the sound travels, the greater the attenuation (and the weaker the beam becomes)
How is attenuation related to frequency?
Directly related
What contributes to attenuation?
Reflection, scattering, absorption
What term(s) describes the redirection of sound in many directions?
Scattering
impedance is equal to…
Density (kg/m^3) • Propagation Speed (m/s)
How is Rayleigh scattering related to frequency?
Proportional to frequency ^4
When frequency doubles- Rayleigh scattering is 16 times greater
