Which configuration uses a transducer and receiver on opposite sides of the test piece to detect flaws by transmitted energy?

• A. Angle beam
• B. Straight beam
• C. Through-transmission
• D. Dual crystal

Answer: (C)

Through-transmission tests place the transmitter on one surface and the receiver on the opposite surface, so energy travels completely through the part. If a defect lies in the path, it blocks or scatters some of that energy, and the receiver on the far side detects a reduced or altered signal. This setup requires access to both faces and is ideal for spotting internal flaws that affect energy transmission across the thickness. It differs from reflection-based methods, where flaws are detected by energy that bounces back to the same side after hitting a flaw. Dual crystal, by contrast, uses transmitter and receiver in close proximity on the same surface, not opposite sides.