Edward J. O'Neill, age 12, of Sandy Hook. Conn., for his question:
HOW DOES A MICROWAVE OVEN WORK?
Microwave energy used in cooking ovens consists of waves we cannot see. The process of emitting energy in the form of waves is known as radiation. The waves travel at the speed of light 186,283 miles per second. They carry bunches of energy which we call photons and which vibrate at various frequencies.
A microwave oven cooks by means of dielectric loss. Food materials are poor electrical conductors and take energy from the microwaves and convert it to heat. These microwaves penetrate deeply into the food material giving up energy as they penetrate.
This energy causes the molecules of the food to vibrate 2,450 million times each second, and thus creating an intermolecular friction which results in heat and accomplishes the cooking action.
Microwave energy is reflected. Metals reflect microwaves and the waves will not penetrate them, nor can they transmit heat. For this reason metal utensils used in cooking the food in conventional gas or electric ovens or on top of the range are not suitable for microwave cooking.
A microwave oven is constructed of metal. The walls of the cavity are built so that they can reflect microwaves in many paths within the cavity. The power supply converts low voltage line power to high voltages required by the microwave energy generator, the magnetron. W
hen the magnetron is energized, it generates high frequency energy which then passes down the waveguide to the oven's cavity.
A mode stirrer turns and interrupts the energy as it enters the cavity and causes it to be distributed all over the inside of the cavity before it is absorbed by the food. Without the mode stirrer, only straight waves would enter the cavity and the food would not cook evenly.
The important characteristic of the microwaves is that they penetrate deeply into the food and produce heat immediately. The utensils remain cool to the touch and food can usually be removed without using a potholder.
Microwave ovens require either 115 or 220 volts, depending on' the model. In most cases they will present no strain on available power.
Microwave ovens are very popular these days. One of the models most often purchased is the portable countertop unit. It operates on 115 volts and does not require special wiring. Those who use the oven, however, should take care not to overload the line with the addition of other appliances.