Briefly state the working principle of microwave ovens.

Explanation

It is observed that the frequency of rotation of water molecules is about `3GHZ (3xx10^(@)Hz)`. If water receives microwaves of this frequency, its molecules absorb this radiation. In a microwave oven the frequency of the microwaves is selected to match the resonant frequency (i.e., 3 GHz) of water molecules so that energy from the microwaves is transferred efficiently to the kinetic energy of water molecules. As a result, water is heated up. Water molecules share this energy with neighbouring food molecules, heating up the food.