Which of the following crystal is mostly present in X-ray
film?
X-ray film has two principal components: (1) emulsion and (2) base. The emulsion, which is sensitive to X-rays and visible light, records the radiographic image. The base is a plastic supporting material onto which the emulsion is coated. 
The two principal components of emulsion are silver halide grains, which are sensitive to X-radiation and visible light, and a vehicle matrix in which the crystals are suspended. The silver halide grains are composed primarily of crystals of silver bromide.
KBr
KI
AgBr
AgI