Question

(a) On a day when the intensity of sunlight is 1.00kW/m2, 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 °C/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.

Answer 1

The initial rate of heating of the water can be calculated using the formula: Q = mcΔT. The polarizing filters get hot because they absorb some of the lost energy from the sunlight.

Step-by-step explanation:

The initial rate of heating of the water can be calculated using the formula: Q = mcΔT, where Q is the heat energy, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.

First, we need to calculate the heat energy received by the water by multiplying the intensity of sunlight (1.00 kW/m²) by the area of the lens (πr²), where r is the radius of the lens. The lens diameter is given as 0.200 m, so the radius is 0.200/2 = 0.100 m.

Then, we multiply the heat energy by the absorption percentage (80.0%) to find the heat energy absorbed by the water. Finally, we divide the absorbed heat energy by the product of the mass of the water and the specific heat capacity of water to find the initial rate of heating in °C/s.

(b) Yes, the polarizing filters get hot because they absorb some of the lost energy from the sunlight.