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The reaction centre in PS II has an absorption maxima at
The reaction centre chlorophyll a of PS II absorbs light maximally at 680 nm (called P680), whereas the reaction centre of PS I absorbs maximally at 700 nm (called P700)!
Photosystems comprise hundreds of pigment molecules bound to proteins forming antennae that funnel excitation energy to a unique single chlorophyll reaction centre:
The two photosystems are designated based on the red absorption peak wavelength of their respective reaction centre chlorophyll molecules:
NCERT states verbatim: "In PS II the reaction centre chlorophyll a has an absorption peak at 680 nm, and is called P680."
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780 nm lies in the near-infrared region, outside the photosynthetically active radiation (PAR, 400-700 nm) spectrum of oxygenic phototrophs.
Exact NCERT peak absorption wavelength for the chlorophyll a reaction centre of PS II ().
700 nm is the absorption peak of Photosystem I (), not Photosystem II.
660 nm is the absorption peak for the red-absorbing form of phytochrome (), not the PS II reaction centre.
PS II acts first in non-cyclic electron transport (Z-scheme), but was discovered second, causing students to associate PS II with 700 nm and PS I with 680 nm.
"In PS II the reaction centre chlorophyll a has an absorption peak at 680 nm, and is called P680."
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