What is the term for the ability of a material to block or partially block the passage of x-ray and gamma rays?

The term that describes the ability of a material to block or partially block the passage of x-ray and gamma rays is "absorption." When x-rays or gamma rays encounter a material, they can be absorbed by the material, which means that the energy of the radiation is taken up by the atoms of that material. This process is crucial in radiographic testing, as it determines how well different materials can be distinguished on a radiographic image.

Absorption is influenced by the material's density and atomic number, with denser materials and those with higher atomic numbers generally providing greater levels of absorption. In radiographic imaging, this characteristic allows for the identification of defects and variations in materials, as areas with different absorption rates will appear differently on the radiograph.

The other terms, while related to the interaction of radiation with materials, describe different phenomena. Reflection refers to the bouncing back of radiation when it encounters a surface, scattering involves the deflection of radiation in various directions, and diffusion describes the spreading out of radiation without directionality. The concept of absorption is key in understanding how radiographic images are formed and how materials interact with ionizing radiation.