instrument consisting of a surface containing chemicals called phosphors that glow when struck by X rays or gamma rays; it is used to transform images made up of invisible radiations into visible light. In a procedure called fluoroscopy, a beam of penetrating radiation is passed through parts of the body; transmitted radiation forms an image of the internal organs in motion on a screen for viewing. Fluoroscopes are also used for the examination of, and search for flaws in, raw and manufactured materials and welded joints.