3: Sound Wave Form Flashcards
When does mode conversion happen?
When an incident beam strikes the interface at an angle other than 0 degrees.
What is mode conversion?
Splitting of the sound beam into different particle displacements (respective to propagation of the wave).
2 conditions required for mode conversion:
- Incident beam must hit an interface between materials of different acoustic properties.
- Incident angle must not be 0 degrees.
When mode conversion splits the reflected waves, the angle of reflection is different. Why?
They travel at different velocities.
Refraction only occurs when…
The wave crosses an interface.
We have reached the first critical angle when…
The incident angle has become large enough that the longitudinal wave moves to the surface of the part.
What is the first critical angle?
The minimum INCIDENT ANGLE required to produce 90 degree refraction angle of the longitudinal wave.
Why are lucite shoes generally cut at an angle that is past the first critical angle?
To avoid having two different waves in the material.
What is the second critical angle?
When we continue to increase the incident angle, and the shear wave moves to the surface.
When calculating the first critical angle, which velocity do you use?
Longitudinal
When calculating the second critical angle, which velocity do you use?
Shear
When calculating critical angles, what is the refracted angle?
90 degrees
What do theta3 and V3 represent in the formula?
Shear wave angle and velocity
What happens to the refracted waves when the incident angle is smaller than the first critical angle?
Longitudinal and shear refracted waves are present in the second medium.
What happens when the incident angle is between the first and second critical angle?
Only shear refracted waves are present in the second medium.
