Microwave ovens, or microwaves, are kitchen appliances which use microwave radiation to cook, heat or defrost food.
Properties of a microwave:
Microwaves are electromagnetic waves with wavelengths longer than those of Terahertz (THz) wavelengths, but relatively short for radio waves. Microwaves have wavelengths approximately in the range of 30 cm (frequency = 1 GHz) to 1 mm (300 GHz). The word microwave generally refers to "alternating current signals with frequencies between 300 MHz (3 x 108 Hz) and 300 GHz (3 x 1011 Hz)."
History of the microwave oven:
The microwave oven was first invented by Dr. Percy Spencer who was a self taught engineer in 1946. He discovered that a magnetron tube which was a new type of vacuum tube, could melt things. He conducted an experiment by placing some popcorn kernels near the tube and found that the kernels near the tube cracked and popped. He attributed this result to exposure to low-density microwave energy. Dr. Spencer created a metal box with an opening into which he fed microwave power, thus creating a higher density electromagnetic field. When food was placed in the box and microwave energy powered up, the temperature of the food rose rapidly. In 1947, the first commercial microwave oven hit the market. These first models were said to be gigantic and enormously expensive, standing 1.67 meters tall, weighing over 340 kilograms and costing about $5000USD each.
Further improvements and refinements soon produced a more reliable and lightweight microwave oven that was not only less expensive, but with the development of a new air cooled magnetron, there was no longer any need for a plumber.
The microwave ovens used in domestic and commercial kitchens are vastly superior to the earlier models. A microwave oven consists of a:
magnetron control circuit (usually with a microcontroller) •
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