The light from each of two 800 W tungsten lamps is filtered so that one lamp gives Light 1 (which is red) and the other gives Light 2 (which is orange). Two separate silicon photovoltaic cells convert the energy from these lights back into electricity. The photovoltaic cells are screened with the same coloured filters as the lamps, making analogues of chloroplast photosystems I and II. When the two cells are connected in series, their output voltages are summed, giving sufficient potential to drive an electric motor.
However, each light on its own will not drive the motor. Why? Because of the series connection - the current through the cell receiving its own colour light must be equal to the current in the other cell. In other words, when one cell absorbs light at its prefered wavelength (colour) then its current still cannot exceed that of the other. Therefore the speed of the electric motor with both lights exceeds the sum of its speeds with each light alone.
Thinking outside the green box | A ten-minute movie clip