Which of the following affects the resolution in PAUT?

The frequency of the ultrasonic waves significantly impacts the resolution in Phased Array Ultrasonic Testing (PAUT). Higher frequencies lead to shorter wavelengths, which result in improved resolution. This means that finer details in the tested material can be detected, making it easier to distinguish between defects or irregularities.

In PAUT, resolution is a critical factor because it determines the system's ability to resolve closely spaced reflectors. Using high-frequency ultrasonic waves enhances the capability to identify smaller flaws, thus providing a more accurate assessment of the material's integrity. It also means that smaller defects can be characterized at greater distances as long as the attenuation of the waves is appropriately accounted for.

While other factors like the thickness of the material, the angle of the inspection beam, and the operator's training do play roles in the overall performance of the testing method, they do not directly influence the resolution as drastically as frequency does. The material's thickness and inspection angle can affect the depth of penetration and the geometry of sound waves, while an operator's training influences the interpretation and execution of the test rather than the fundamental physical properties of the ultrasonic waves themselves.