The quantum efficiency of photosynthesis measurement in green plants indicated that 8 quanta of red light at 6850Ao are required to evolve one molecule of oxygen. The average energy storage in the photo-synthetic process is 112 k cal mol- O2 evolved. Calculate the energy conversion efficiency in the experiment.

λ=6850Ao=6850×10−10m;h=6.63×10−34Js. We know that :E=hcλThus, E=6.63×10−34Js×3.0×108ms−6850×10−10mor E=2.9×10−19J8 quanta means, E=8×2.9×10−19J=23.2×10−19JAverage energy stored=112kcalmol×4184J1kcal×1mol6.02×1023molecules=7.78×10−19J/molecule∵1kcal=4184J;1mol=6.02×1023 molecules ∴ Energy conversion efficiency=7.78×10−19J molecule ×123.2×10−19J×100=33.53%