Defects such as cracks and porosity show up as what type of shadows in radiographic inspection?

In radiographic inspection, defects like cracks and porosity are represented as darker shadows on photographic paper. This phenomenon occurs because these defects disrupt the path of the radiation being used for imaging. When radiation passes through a material, areas that are denser or without defects will absorb more radiation and appear lighter on the photographic film. Conversely, areas with defects allow more radiation to penetrate through, resulting in darker regions on the film where the weaker or unabsorbed radiation has reached.

This principle is fundamental in non-destructive testing and radiography, as it helps technicians identify and assess the integrity of materials by examining the resultant images. The contrast between the darker and lighter areas thus provides crucial information about potential flaws in the material being tested.