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Q:- The metal whose salts are sensitive to light is?
(A) Zinc
(B) Silver
(C) Copper
(D) Aluminium
Answer:- B
Explanation:- An amount in which an element reacts when it receives photons, specifically when it receives visible light is known as photosensitivity. The elements which can undergo photochemical reactions are known as photosensitive elements.
The photochemical reaction can be further divided into 3 categories as follows:-
Reactions of elements in which the yield is a small integer such as 1,2 or 3. Example:- dissociation of hydrogen iodide and hydrogen bromide.
Reactions of elements whose quantum yield is less than 1. Example:- dissociation reaction of nitrogen dioxide.
Reactions of elements whose quantum yield is extremely high. Example:- the combination reaction of chlorine and hydrogen.
One of the most important examples of photochemical reactions are reactions which involve the salts of silver metal, specifically silver halides which are light-sensitive and therefore undergo a photographic process. When halides are exposed to light, they undergo a chemical reaction which darkens the film to generate an image. Therefore these compounds are used to make images.
The silver chloride crystals contain tightly packed ions which are Ag⁺ and Cl⁻. When the film is exposed the additional electron of chlorine ions gets excited and is ejected which are seized by silver ions and get converted into silver metal. When silver metal is formed as a product of this reaction the whole crystal is converted into metallic silver and it results in the formation of an image on the film.
Silver bromide and iodide were very important in the history of photography because of their sensitivity to light. Even in the recent world with the rise in digital photography, silver salts are still very important in making high-quality images and protecting against illegal copyright. In this reaction, the brighter the light which falls on the photographic paper or film, the faster the reactions take place and the darker the image appears.
Therefore silver metal is sensitive to light.
