Halogen: Halogens are a group of five elements in the periodic table (fluorine, chlorine, bromine, iodine, and astatine) that are highly reactive nonmetals.
Photographic Film: Photographic film is a thin, flexible plastic strip or sheet coated with a light-sensitive emulsion, used to capture images in a camera.
Photographic Plate: A photographic plate is a flat piece of glass or other transparent material coated with a light-sensitive emulsion, used to capture images in early photography.