1.7 Exercise 37

(a) On a day when the intensity of sunlight is $1.00 \text{kW}/\text{m}^{2}$, a circular lens 0.200 m in diameter focuses light onto water in a black beaker. Two polarizing sheets of plastic are placed in front of the lens with their axes at an angle of $20.0 °$. Assuming the sunlight is unpolarized and the polarizers are $100 \%$ efficient, what is the initial rate of heating of the water in $° \text{C}/\text{s}$, assuming it is $80.0 \%$ absorbed? The aluminum beaker has a mass of 30.0 grams and contains 250 grams of water. (b) Do the polarizing filters get hot? Explain.