Question

Why does microwave oven heat up a food item containing water molecules most efficiently?

Answer 1

The waves produced by microwave oven heats food. These waves have frequency equal to the resonating frequency of water molecules. As all food items have water, the water molecules absorb energy from these waves and start vibrating. This vibration produces heat, and the food gets heated. Thus, food items having excess water will be heated most efficiently.

Final answer: Frequency of the microwave matches the resonant frequency of water molecules.