Q1: Hypo (sodium thiosulphate) because of its complex forming behaviour is used in photography to remove undecomposed silver bromide as a soluble complex for __________ of the picture.

ANS:B - developing

Sodium thiosulfate (hypo) is used in photography for the fixation of the picture, not for developing it. Explanation:

1. Developing in Photography: Developing is a crucial step in traditional film photography where the latent image captured on the film's emulsion during exposure to light is made visible. This process involves chemical reactions that convert the exposed silver halide crystals (such as silver bromide) into metallic silver, forming the visible image.
2. Purpose of Fixation: After the film has been developed, it contains both developed silver grains (which form the visible image) and undecomposed silver halide crystals that were not exposed to light. These undecomposed silver halide crystals are light-sensitive and must be removed to prevent them from causing fogging or unwanted background on the final image. This removal process is known as fixation.
3. Role of Sodium Thiosulfate (Hypo): Sodium thiosulfate, commonly known as hypo, is used in the fixing bath during the photographic process. It acts as a fixer by dissolving the undecomposed silver halide crystals, particularly silver bromide, to form soluble complexes. These complexes are then washed away from the film during the fixing process, leaving behind only the developed silver image.
4. Printing and Developing: Printing and developing are earlier stages in the photographic process. Developing involves the chemical reaction that transforms the latent image into a visible image on the film. Sodium thiosulfate (hypo) is not involved in the developing process; it is specifically used for fixation after development.