The distance between two consecutive points in a wave that are in phase, such as the distance between two peaks or two troughs of a wave. In non-destructive testing, wavelength is often used to determine the resolution and diffraction characteristics of waves.

The vertical distance or depth of water or liquid couplant used in immersion testing, typically measured from the transducer face to the surface of the liquid column, influencing the wave propagation and acoustic coupling during ultrasonic inspections.

A concept used in PAUT where the phased array system virtually simulates a single-element transducer at a specific location within the array. Instead of physically moving a single transducer to different positions, the virtual probe allows for the electronic manipulation of the ultrasonic beam characteristics.

A medium or substance, often a gel, oil, or water-based solution, used to facilitate the transmission of ultrasonic waves between a transducer and the surface or interface of a test object, ensuring efficient energy transfer and wave propagation.

A type of wave motion where the displacement of particles or energy is perpendicular or transverse to the direction of wave propagation.

A device or sensor that converts one form of energy into another, such as an ultrasonic transducer that converts electrical energy into ultrasonic waves or an electromagnetic transducer that converts mechanical vibrations into electrical signals.

An advanced ultrasonic array technique utilized to achieve synthetic focusing at every individual point within a specified region of interest to create high-resolution images. By considering the individual wave contributions from various angles and positions, TFM technology allows for precise focusing and imaging at each location. 

A reference or scale used to measure and display time-related informations, such as the time-axis on a waveform display or the time settings for pulse repetition frequency or gate positioning.

The time it takes for a wave or signal, such as an ultrasonic pulse or electromagnetic wave, to travel a specific distance through a material or medium, often used to determine the depth or position of a discontinuity.

A method where ultrasonic energy is transmitted through the test object and detected by a second transducer positioned on the opposite side. Variations in the amplitude of the received signal are used as indicators of material continuity differences.