Photographic plates are coated with a thin layer of which compound?

Photographic plates are used to capture images by recording light exposure. The light-sensitive material on these plates is a silver halide, which undergoes a chemical change when exposed to light. The most commonly used compound for coating photographic plates is silver bromide (AgBr).

Silver bromide is a pale yellow solid that is highly sensitive to light. When light falls on AgBr, it decomposes to produce elemental silver and bromine, creating a latent image. This latent image can then be developed using chemical developers to produce a visible photograph. The sensitivity of silver bromide to light makes it ideal for capturing fine photographic details.

Other silver compounds like silver nitrate (AgNO₃), silver iodide (AgI), and silver chloride (AgCl) are also light-sensitive but are used for specific applications. Silver iodide is mainly used in cloud seeding and some specialized photographic emulsions. Silver chloride is used in some photographic papers and for producing images in black-and-white photography, but it is less sensitive than silver bromide. Silver nitrate is primarily a laboratory reagent and is not used directly for coating plates.

Silver bromide’s chemical formula is AgBr. It belongs to the class of inorganic ionic compounds known as halides. Its light sensitivity and stability make it central to traditional photographic techniques. Understanding silver halides and their reactions with light helps students learn about photochemistry, inorganic compounds, and historical photographic processes.

This question highlights the application of inorganic chemistry in photography and demonstrates how the chemical properties of silver halides are utilized in practical technology.