Extra exam question E6F09

WhyA photovoltaic cell's efficiency is the relative fraction of light that is converted to current. A photovoltaic cell's efficiency is defined as the relative fraction of the light energy striking it that actually gets converted into usable electrical current, a measure of how much of the available sunlight the cell manages to capture and convert rather than lose, answer D. It isn't an RF power ratio, isn't measured in lumens per watt, and isn't simply open-circuit voltage divided by short-circuit current, those don't define efficiency the way this question describes it.