The halide that is widely used in photography is silver bromide. Halides are compounds that contain halogen elements like bromine, chlorine, iodine, etc. In photography, halides are used to make light-sensitive materials. Silver bromide is particularly useful because it is sensitive to light and can be used to capture images.
When light falls on a film or photographic paper containing silver bromide, the silver ions in the compound are reduced to form silver metal. This forms the basis of photographic development, where the image is created through a chemical reaction between the light-sensitive material and a developing agent.
In summary, silver bromide is the halide used in photography because of its light sensitivity and its ability to form a visible image through a chemical reaction with a developing agent.