High energy electromagnetic waves (radiation) penetrating to a particular material can also affect radiation sensitive films placed on the other side of the material. When these films are subjected to the bath process, the interior of the material passes through the radiation is exposed. This image occurs because of gaps or changes in thickness / density within the material. The process of visualizing the material in this way is called radiographic inspection. It can be used to detect expected volume and surface defects in all metallic or non-metallic materials.