Which element is essential for electron transport during the process of photosynthesis?

Proton gradient is very important across the membrane because

Which one of the following concerns photophosphorylation?

How many molecules of water should be photolysed to form one $NADPH_2$ molecule?

The following $(I-VI)$ are the main steps of chemiosmotic $ATP$ synthesis in the light reaction. Arrange them in the correct order:
$I$. $H^+$ concentration gradient established
$II$. $H^+$ diffuses through $ATP$ synthase
$III$. Carriers use energy from electrons to move $H^+$ across the membrane
$IV$. Electrons from $PS-II$ pass along the electron transport chain
$V$. Light excites electrons in $PS-II$
$VI$. Energy of $H^+$ flow is used by $ATP$ synthase to make $ATP$

The most effective wavelength of visible light in photosynthesis is in the region of