Question

The defects in metal blocks are generally detected using

• A. Audible sound waves
• B. Infrasonic sound waves
• C. Ultrasonic sound waves
• D. Supersonic sound waves

Answer 1

The correct option is C Ultrasonic sound waves

Metallic blocks are generally used in making large structures like machines, bridges and buildings. There might be holes or cracks in the metallic blocks. If not rectified, it may cause accidents. The ultrasonic sound waves are allowed to pass through the metal blocks. There are detectors placed on the other side of the metal blocks, which are used to detect the transmitted wave. In this way, defects/cracks in metal blocks are detected.

Thus, to detect the defects in the metal blocks, ultrasonic sound waves are used. The frequency of ultrasonic sound is more than 20 kHz.

Hence, the correct answer is option (c).