3. In the photoelectric effect experiment, the graph of current vs battery voltage for a metal with light of a particular frequency shining on it looks like the curve below. This graph represents current vs voltage for 200 nm light shining onto Cadmium (Cd) which has a work function of 4.07 eV. Explain your reasoning for why this curve has the shape that it does. In your answer, you should address: Why is current level at V>0, why does current go to zero at some negative voltage and what determines that voltage, and why does current start decrease steadily at V