The method of cooking food by microwave was first thought of by Percy Spencer, who works for Raytheon Company. Percy Spencer used to make magnetrons for the company's radar equipment. One day, while he was studying an activated radar device, he suddenly found that the chocolate he had put in his pocket had melted. After thinking and studying, Percy Spencer found that his chocolate was melted by microwave, so he thought that magnetron could also be used for cooking.
The working principle of microwave oven is that food molecules can be divided into polar molecules and nonpolar molecules when irradiated by microwave (frequency is often 2.45 GHz). Under the action of external electric field, the originally disordered polar molecules turn along the direction of external electric field, resulting in turning polarization; Polar molecules produce displacement polarization along the direction of external electric field. When the direction of applied electric field changes, the direction of molecular rotational polarization or displacement polarization also changes. When the microwave oven is working, the food molecules placed in the oven are polarized (i.e. swung) back and forth more than 2.4 billion times per second under the action of microwaves (i.e. high-frequency alternating electromagnetic fields). At this time, the collision and friction between molecules convert electromagnetic energy into heat energy, which makes the internal and external temperatures of food rise at the same time in a very short time, so that the food can be heated quickly without destroying various vitamins and nutrients beneficial to human body, and it is bright in color and delicious in taste.