What is Incident Intensity?

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

What is Reflected Intensity?

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

What is Transmitted Intensity?

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.

What are the units of all intensities?

W/cm^{2}

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

Incident intensity = reflected intensity + transmitted intensity

What happens to ultrasound energy?

(e.i., what causes attenuation?)

Reflection

Scattering

Absorption

Most ultrasound energy is lost to _______?

Absorption

What is the interface?

The boundary between two media having different acoustic Z.

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

Echos are created by ___?

Zero. No echo.

∆Z

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

Bigger ∆Z, means more reflection:

Stronger echo. Very little transmission.

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

Not much reflects. Small echo.

A lot transmits.

At a boundary between two soft tissues, a very

big ∆Z means:

Very big echo. Reflection is near total.

Very little transmits.

What is normal incidence?

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

Some synonyms for normal incidence are:

Perpendicular. Orthogonal.

Right angle. 90 degrees.

When does oblique incidence occur?

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

True or false:

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

False.

The angle must **not** equal 90º.

What does oblique mean?

Not at right angles or perpendicular.

What type of incidence is this?

Sound striking a boundary at normal incidence.

What type of incidence is this?

Sound striking a boundary with oblique incidence.

What is IRC?

Intensity Reflection Coefficient;

the proportion (percentage) of intensity

that is reflected.

What is ITC?

Intensity Transmission Coefficient;

the proportion (percentage) of intensity

that travels on beyond the interface.

What is a coeffiecient?

A number that relates variables;

a constant relationship.

Name two ways to find IRC:

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- You know the impedances of the two media
- You know the intensities of the two media

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

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

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

Incident intensity

If the IRC and ITC are added,

the result must ____ ____.

Must equal 100%

A sound wave with a intensity of 50 W/cm^{2} strikes a boundary and is toally reflected.

What is the intensity reflection coefficient?

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

A sound wave with an intensity of 50 W/cm^{2} strikes a boundary and is totally reflected.

What is the reflected intensity?

Since the wave is totally reflected,

**intensity** is 50 W/cm^{2}.

What is the equation used to calculate

**i**ntensity **r**eflection **c**oefficient when given the impedances?

What is the equation used to calculate

**i**ntensity **t**ransmitted **c**oefficient when given the intensities?