Final answer:
Longitudinal waves occur in fluids where the particles vibrate parallel to the wave direction, typical of sound waves in air and water. Shear, or transverse waves, occur in solids where the particles move perpendicular to the wave direction and are utilized in ultrasonic testing along with longitudinal waves.
Step-by-step explanation:
Longitudinal and shear waves are mode of vibrations in different media. In fluids such as air and water, sound waves are inherently longitudinal due to the absence of shear strength. The particles of the medium in a longitudinal wave oscillate parallel to the direction of wave propagation. This results in periodic compressions and rarefactions in the medium. On the other hand, solids support shear waves, also known as transverse waves, where the particles of the medium move perpendicular to the direction of wave propagation.
Ultrasonic testing, an industrial and medical application, often requires the generation of both longitudinal and shear waves to detect flaws in materials or to image internal organs. These high-frequency sound waves are produced by converting electrical energy into mechanical vibrations with the use of a piezoelectric transducer. The type of wave produced depends on the angle and the mode of vibration induced in the medium, which can be adjusted according to the testing requirements.