* Take one drop of the suspension of white silver chloride (obtained in the previous
   experiment) into the sun light.
* Place it into bright sun light while a second drop is kept dark by a black film canister.
Observation (Photo): A black precipitate is formed where light has access.
Explanationm: This is another example of a  redox reaction:
At any place reached by the light (Greec: phos) an electron transfer takes place from the negative chloride ions [Cl^-] to the  positive silver ions (Ag⁺).
Silver ions are reduced to silver atoms forming a lattice at the black spots.