what term means source of oxygen atoms in glucose formed by photosynthesis?

Answer 1

I would say it is the leaf of a plant or the plant itself. The leaf gives off oxygen (the waste product) during photosynthesis.

Or: (I grabbed this off Wikipedia)
photosynthesis uses water as an electron donor which is oxidized into molecular oxygen by the absorption of a photon by the photosynthetic reaction centre.

Answer 2

The oxygen atoms in the glucose comes from the water not the carbondioxide.