A solar cell generates a potential difference of .1 V when a 500 ohm resistor is connected across it and a potential difference of .15 V when a 1000 ohm resistor is substituted. What are the internal resistance and emf of the solar cell? IF the area of the cell is 5 cm^2 and the rate per unit area at which it receives energy from light is 2 mW/cm^2. What is the efficiency of the cell for converting light energy to thermal energy in the 1000 ohm resistor?