During straight beam testing, non-parallel front and back surfaces can cause which effect (alternative wording)?

• A. Partial or total loss of back reflection
• B. Increased back reflection
• C. No change in back reflection
• D. Narrowed back reflection

Answer: (A)

When performing straight-beam testing, the transducer sends a pulse straight into the material and looks for reflections that return along the same path, especially from the back surface. If the front and back surfaces are parallel, the reflection from the back surface travels back toward the transducer, producing a clear back-wall echo.

If the front and back surfaces are not parallel, that back-surface reflection is angled away from the transducer. The energy that would return to the probe is deflected, so much of it doesn’t come back to be detected. That reduces the back reflection, and in some cases the back-wall echo can be partially or completely lost. So the effect you’d observe is a partial or total loss of back reflection.

The other options don’t match this geometry-driven outcome: the non-parallel surfaces don’t typically increase the back reflection, nor do they leave it unchanged, and they don’t inherently produce a narrowed back echo.