Non-Destructive Testing (NDT) Practice Test

Which type of wave is characterized by straight-line propagation used in ultrasonic testing?

1. Transverse Wave

2. Longitudinal Wave

3. Surface Wave

4. Guided Wave

The correct answer is: Longitudinal Wave

In ultrasonic testing, the type of wave that is characterized by straight-line propagation is the longitudinal wave. Longitudinal waves are mechanical waves where the particle displacement is parallel to the direction of wave propagation. This means that as the wave travels through a medium, such as metal or any solid material, the molecules of the medium move back and forth in the same direction as the wave is moving. This characteristic of longitudinal waves allows them to effectively penetrate materials and is fundamental to ultrasonic testing methods. These waves can travel efficiently through solid materials and are primarily used in ultrasonic testing to detect internal flaws, measure the thickness of materials, and perform various inspections without causing damage. Other types of waves, such as transverse waves, surface waves, and guided waves, have different propagation characteristics. Transverse waves move perpendicular to the direction of propagation and cannot travel through liquids or gases. Surface waves travel along the surface of a material and typically have distinct applications in different contexts, such as seismic studies. Guided waves are confined to specific structures and can travel longer distances but are not characterized by straightforward propagation compared to longitudinal waves.