Under controlled darkened conditions in the laboratory, alight receptor cell on the retina of a person's eye can detect a single photon of light of wavelength 505nm and having an energy of 3.94x10^-19 J. We shall assume that this energy is absorbed by a single cell during one period of the wave. Cells of this kind are called rods and have a diameter of approximately 0.0020mm. What is the intensity (in W/m^2) delivered to a rod?