Review. Model the electromagnetic wave in a microwave oven

Chapter 34, Problem 26

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Model the electromagnetic wave in a microwave oven as a plane traveling wave moving to the left, with an intensity of \(25.0 \mathrm{~kW} / \mathrm{m}^{2}\). An oven contains two cubical containers of small mass, each full of water. One has an edge length of 6.00 cm, and the other, 12.0 cm. Energy falls perpendicularly on one face of each container. The water in the smaller container absorbs 70.0% of the energy that falls on it. The water in the larger container absorbs 91.0%. That is, the fraction 0.300 of the incoming microwave energy passes through a 6.00-cm thickness of water, and the fraction \((0.300)(0.300)=0.090\) passes through a 12.0-cm thickness. Assume a negligible amount of energy leaves either container by heat. Find the temperature change of the water in each container over a time interval of 480 s.