Science Buddies: "Ask an Expert"

Help! My daughter is conducting a science project where she measures the power output of a solar panel at different angles of incoming light. She has completed her measurements but we are uncertain about the results. She maintained the light source at a constant height and distance from the solar panel. She varied the angle of the solar panel and measured the Voltage of the open circuit and the current to get the power output. The amps varied as we expected; however, the voltage also varied at different angles. Is this correct?

Since I assume the load is constant, the only other variable must be voltage. Hence, the variation in voltage is correct.