There are two reasons why light is important for this phase. What does it do for the PS II phase?
Photosystem II uses light energy to drive two chemical reactions - the oxidation of water and the reduction of plastoquinone. Being absorbed by pigments energy is passed inward from pigment to pigment until it reaches the reaction center, where high energy electron is replaced with an electron from water releasing O2. Therefore, Photosystem II Transfers Electrons from Water to Plastoquinone.