Which term describes the ability of an ultrasonic testing system to differentiate between entry surface response and responses of nearby discontinuities?

The term that accurately describes the ability of an ultrasonic testing system to differentiate between the entry surface response and the responses of nearby discontinuities is resolution. Resolution refers to the capacity of a testing system to distinguish between two closely spaced reflectors or features within the material being examined. In ultrasonic testing, high resolution is crucial for identifying and characterizing flaws, allowing the operator to discern the reflections from the entry surface and those from any imperfections within the material.

In this context, while clarity, definition, and contrast might seem relevant, they do not specifically capture the technical aspect of distinguishing between signals generated by different sources within the material. Clarity often pertains to the overall visibility of the data on the display, definition might suggest the detail present, and contrast typically relates to the difference in signal amplitudes rather than the spatial differentiation required for resolving closely spaced returns. Thus, resolution is the precise term for this capability in ultrasonic testing.