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Physics 110 Exam 2 > Beams, interfaces, reflection, refraction > Flashcards

Beams, interfaces, reflection, refraction Flashcards

1
Q

What is Incident Intensity?

A

The sound wave’s intensity immediately before it strikes a boundary.

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2
Q

What is Reflected Intensity?

A

The intensity of the portion of the incident sound beam that, after striking a boundary, returns back from where it came.

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3
Q

What is Transmitted Intensity?

A

The intensity of the portion of the incident beam that, after striking a boundary, continues forward in the same general direction that is was traveling.

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4
Q

What are the units of all intensities?

A

W/cm2

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5
Q

There is conservation of energy at the boundary. How does this affect incident (starting) intensity?

A

Incident intensity = reflected intensity + transmitted intensity

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6
Q

What happens to ultrasound energy?

(e.i., what causes attenuation?)

A

Reflection

Scattering

Absorption

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7
Q

Most ultrasound energy is lost to _______?

A

Absorption

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8
Q

What is the interface?

A

The boundary between two media having different acoustic Z.

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9
Q

If the two media are the same Z, what is the reflection?

Echos are created by ___?

A

Zero. No echo.

∆Z

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10
Q

If the two media have a very big ∆Z, how does this affect the echo?

A

Bigger ∆Z, means more reflection:

Stronger echo. Very little transmission.

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11
Q

At a boundary between two soft tissues, a small ∆Z means:

A

Not much reflects. Small echo.

A lot transmits.

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12
Q

At a boundary between two soft tissues, a very

big ∆Z means:

A

Very big echo. Reflection is near total.

Very little transmits.

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13
Q

What is normal incidence?

A

When the incidence sound beam strikes the boundary at exactly 90º.

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14
Q

Some synonyms for normal incidence are:

A

Perpendicular. Orthogonal.

Right angle. 90 degrees.

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15
Q

When does oblique incidence occur?

A

When the incident sound beam strikes the boundary at any angle other than 90º.

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16
Q

True or false:

For incidence to be oblique, the angle must equal 90º.

A

False.

The angle must not equal 90º.

17
Q

What does oblique mean?

A

Not at right angles or perpendicular.

18
Q

What type of incidence is this?

A

Sound striking a boundary at normal incidence.

19
Q

What type of incidence is this?

A

Sound striking a boundary with oblique incidence.

20
Q

What is IRC?

A

Intensity Reflection Coefficient;

the proportion (percentage) of intensity

that is reflected.

21
Q

What is ITC?

A

Intensity Transmission Coefficient;

the proportion (percentage) of intensity

that travels on beyond the interface.

22
Q

What is a coeffiecient?

A

A number that relates variables;

a constant relationship.

23
Q

Name two ways to find IRC:

A
  1. You know the impedances of the two media
  2. You know the intensities of the two media
24
Q

As a sound beam strikes a boundary, energy is conserved, and 100% of the intensity must be accounted for. The following relationship applies:

A

100% = IRC (%) + ITC (%)

25
Q

If the reflected and transmitted intensities are added, the result must be the ____ ____.

A

Incident intensity

26
Q

If the IRC and ITC are added,

the result must ____ ____.

A

Must equal 100%

27
Q

A sound wave with a intensity of 50 W/cm2 strikes a boundary and is toally reflected.

What is the intensity reflection coefficient?

A

Since the wave is totally reflected, the intensity reflection coefficient is 100%.

28
Q

A sound wave with an intensity of 50 W/cm2 strikes a boundary and is totally reflected.

What is the reflected intensity?

A

Since the wave is totally reflected,

intensity is 50 W/cm2.

29
Q

What is the equation used to calculate

intensity reflection coefficient when given the impedances?

A
30
Q

What is the equation used to calculate

intensity transmitted coefficient when given the intensities?

A

Physics 110 Exam 2 (6 decks)

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