Electromagnetic waves are generated in the microwave oven, similar to radio or television waves. These microwaves set the smallest components of the food, such as water and fat molecules, in motion so that the molecules rub against each other. This friction in turn generates heat, which cooks the food within a short time.
The inside of the microwave oven has a high-frequency tube, the magnetron, which emits these waves. The microwaves are channelled into the interior of the oven through a metal channel and distributed evenly in the food by means of a rotating plate.
As microwaves are distributed in a straight line in the room, they pass unhindered through glass, porcelain, ceramic, plastic and cardboard and are absorbed by the food. This allows the waves to act directly on the food without wasting energy by heating the containers. Metal shields the microwaves and reflects them, so metal must not be used in the microwave.
Microwaves are long-wave. Long-wave radiation has been used in medical heat therapy for decades. The metal housing of the microwave oven shields the radiation from the environment so that no radiation escapes either when the oven is heated or when it is opened. A safety system ensures that the mechanism is switched off when the door is opened. If the microwave oven is operated correctly, food can be cooked gently so that the nutritional value of the food is largely preserved.
