How does a crack type discontinuity typically appear in penetrant testing?

In penetrant testing, a crack type discontinuity typically appears as a continuous line, which can be either straight or jagged. This is because penetrant testing is designed to reveal surface discontinuities, and cracks will allow the penetrant to seep into the voids, highlighting the exact path of the discontinuity.

When a crack is present, the penetrant will accumulate along the crack's length, making it evident during the development process. This manifested visual representation aids in identifying the location, orientation, and possibly the severity of the crack.

The other options do not accurately describe how a crack-type discontinuity is represented in penetrant testing. A series of dots may indicate surface porosity, while shadows typically indicate issues related to surface texture or contamination; these do not directly relate to crack identification. Lastly, color changes are generally associated with surface conditions or specific flaws but do not provide the clear linear representation that a crack yields.