A solar cell generates a potential difference of 0.10 V when a 500 $\displaystyle \Omega$ resistor is connected across it, and a potential difference of 0.15 V when a 1000 $\displaystyle \Omega$ is substituted. What are the (a) internal resistance and (b)emf of the solar cell? (c) The area of the cell is 5.0 $\displaystyle cm^2$, and the rate per unit area at which it receives energy from light is 2.0 $\displaystyle \frac{mW}{cm^2}$. What is the efficiency of the cell for converting light energy to thermal energy in the 1000 $\displaystyle \Omega$ external resistor?