Attenuation of X-rays
When the x-ray passes through an absorber (e.g., oral tissues), it gets differentially absorbed by what constitutes the absorber and the thickness of each component. When the x-ray beam exits this absorber, it will have varying levels of intensities. This variation will be recorded on a radiographic receptor as different densities generating the radiographic contrast. The densities related to a thick absorber (i.e., aluminum) will be brighter than the densities of the thin absorbers (Figure 8).1,2,3,4,6
Figure 8. Photo and radiographic image of an aluminum stepwedge. The thin steps are darker than the thick steps.