Question

Microwave oven acts on the principle of:
A. giving rotational energy to water molecules
B. giving vibrational energy to water molecules
C. transferring electrons from lower to higher energy levels in the water molecule
D. giving translational energy to water molecules

Answer 1

Hint: Microwave is one of the most widely used household appliances. Today, most homes and restaurants have microwave ovens. These are the most popular because they cook food in a short interval of time. They are also extremely efficient in their use of electricity because it can heat only food and nothing else.

Complete step by step answer:
In 1445, the microwave was accidentally discovered by Percy Spencer, which has a high power heating effect. A microwave oven uses microwaves. In the case of microwave ovens, the commonly used radio waves frequency is roughly 2500MHz. Radio waves in this frequency range have an interesting property:
They are absorbed by water, fats, and sugars. When they are absorbed they are converted directly into atomic motion and motion is converted into heat. Also, they are not absorbed by most plastics, glass, and ceramics.
In microwave cooking, the radio waves penetrate the food and excite water and fats molecules throughout the food. There is no heat having to migrate toward the interior by conduction. There is heat everywhere at all once because the molecules are all excited together. In a microwave oven, the air in the oven is at room temperature, so there is no way to form a crust because it heats up food by microwaves, not by heat conduction.
The microwave has a frequency equal to the resonance of the frequency of water. Therefore food could be heated up by the vibrational water molecules.

$\therefore$ Hence the correct option is (B).

Note:
In microwaves, if a metal spark is generated then no food is heated up. If the food is different in ingredients heating velocity could be different. For instance, the food containing more fat will be heated up fastly. In the microwave heat control is difficult and surface toasting is impossible.