What acts as the activator in the developer or serves as a source of alkali?

The activator in the developer, which serves as a source of alkali, is hydroxide. In the context of photographic development, hydroxide ions contribute to the alkalinity of the developer solution, which is crucial for the reduction of exposed silver halide crystals to metallic silver. This alkaline environment enhances the activity of the developing agents, allowing for a more efficient chemical reaction during the development process.

The presence of hydroxide helps to break down the protective layers around the silver halides, facilitating their conversion and ultimately leading to the formation of the image. This function is vital for the overall performance of the developing process because it ensures that the development is carried out effectively, resulting in clearer and more defined images.