What does a B-scan display illustrate in ultrasonics?

A B-scan display in ultrasonics provides a two-dimensional representation of the internal structure of a material. It effectively shows the distance of a discontinuity from the transducer, as well as its length, by plotting the time it takes for the sound waves to travel through the material and reflect back from any discontinuities. This graphical representation enables operators to visualize where defects are located within the material, alongside their size and orientation.

In contrast, while the speed of sound in the material is important for interpreting ultrasonic data, it is not directly illustrated by a B-scan display. Similarly, while the scan area can be relevant to the overall inspection process, it does not specifically represent the information provided by a B-scan. The identification of the types of discontinuities is derived from interpreting the B-scan data rather than being explicitly shown in the scan itself. Therefore, option B accurately captures the primary function of a B-scan in ultrasonic testing.