Why might natural discontinuities not be detected on a radiograph?

Natural discontinuities, such as voids or inclusions in a material, might not be detected on a radiograph primarily because they do not have sharp edges. The definition of a natural discontinuity refers to an absence of a material in a structured form; these features often display gradual transitions rather than defined borders. This lack of sharp edges can lead to an insufficient contrast on the radiograph to differentiate the discontinuity from the surrounding material, ultimately resulting in its possible oversight by the inspector.

Additionally, while other factors can influence the visibility of discontinuities, such as size or overlapping radiographic artifacts, the key reason for undetected natural discontinuities lies in their indistinct and non-sharp characteristics. This distinction is vital for radiographic inspections, as sharp edges usually present a higher contrast against the background material, making them easier to identify on the film.