Why does green light give a low rate of photosynthesis?

The question is in regard to leafs, as my resident teenager just had the same homework. It is poorly Worded, as it should be asking, "Why does a leaf exhibit a low oxygen flow when illuminated only by green light" ...or something along those lines.

In simple terms, chlorophyll feeds the plant by converting light and CO2 into 'food' and O2. A lack of oxygen means that this chemical reaction isn't occurring. Why? A lack of light. The chlorophyll is green because it primarily reflects green and yellow light, meaning that it absorbs (and uses) the reds and blues. Shining a green light on a plant is almost the same as not shining any light on it.