In hills rxn why was sthe spectrophotometer set to 600nm (orange-red light)?

Question

In hills rxn why was sthe spectrophotometer set to 600nm (orange-red light)?

Answer 1

During the Hill reaction electrons are extracted from water using energy from visible light.  The electrons need somewhere to go.  That is, a chemical electron acceptor molecule must be present.  Typically, this artificial acceptor is a dye that changes color when it gets reduced (takes up an electron).  You did not say what your dye is, but this color change is directly proportional to the number of electrons that have been moved from water to the dye.  Apparently, the dye has an absorption peak at 600 nm so the progress of the Hill reaction will be most sensitively monitored at this wavelength.