Microwave oven, also called electronic oven, appliance that cooks food by means of high-frequency electromagnetic waves called microwaves. A microwave oven is a relatively small, boxlike oven that raises the temperature of food by subjecting it to a high-frequency electromagnetic field. The microwaves are absorbed by water, fats, sugars, and certain other molecules, whose consequent vibrations produce heat. The heating thus occurs inside the food, without warming the surrounding air; this greatly reduces cooking time, and baking and other cooking tasks that require hours in a conventional oven can be completed in minutes in a microwave oven. Microwave ovens generate radiation at a frequency of about 2,450 megahertz by means of a magnetron, which is a kind of electron tube.
Since the heating occurs by an absorption process, microwave ovens tend to cook certain foods unevenly or at different rates. For example, moist foods cook faster than less moist ones, and moist outer layers tend to absorb most of the radiation before it can reach inner sections, which remain uncooked. Microwave ovens also cannot brown or crisp foods on the outside. Most types of glass, Styrofoam (trademark), polyethylene, paper, and similar materials do not absorb the microwaves and hence do not heat up. Foods cannot be cooked in metal vessels in a microwave oven, however, because the metal blocks out the microwaves. Microwave ovens are subject to safety standards that ensure minimal levels of radiation leakage from them, and no significant health hazards are associated with such leakages.
Microwave Oven Essay
These days, in many homes, it is virtually impossible to have a so called modern kitchen, without having a microwave oven in it. The microwave oven could probably occupy the second place (after the refrigerator), in terms of dependence, in the kitchen. This magical piece of technology has revolutionized the way people, and the food industries cook food. The microwave oven is only a natural evolution of technology; to fit into this fast-paced world. As in every evolutionary process, one must look back at the history of how it all began. Then for the scientifically-inclined; the heart of the microwave oven will be revealed, by exposing the physics that make it work. And last, we will present to the reader how these microwaves actually cook the food.
Like many of today's greatest inventions, the microwave oven was a by-product of another technology. The microwave oven did not come about as a result of someone trying to find a better, faster way to cook, but it was an accidental invention! In 1939, Two British scientists, H A H Boot and J T Randall developed the pulse type magnetron tube for radar, a tube that produces microwaves. Installing magnetrons in Britain's radar system, the microwaves were able to spot Nazi warplanes on their way to bomb the British Isles.
A few years later, around 1945, during a radar-related research project; Dr. Percy Spencer, an engineer with the Raytheon Corporation, noticed something very unusual. Dr. Spencer was conducting some tests on the magnetron, when he discovered that the candy bar in his pocket had melted. This intrigued Dr. Spencer, so he tried another experiment. This time he placed some popcorn kernels near the magnetron and he watched as the popcorn cracked and popped all over his lab. An idea was born!
The following day, Dr. Spencer decided to put the magnetron tube near an egg. And he watched as the egg began to tremor and quake. The rapid temperature rise within the egg was causing tremendous internal pressure. Evidently, after a couple of minutes, the egg exploded and splattered hot yolk all over the table. The face of Spencer lit up with a logical scientific conclusion: the melted candy bar, the popcorn, and now the exploding egg, were all attributable to exposure to low-density microwave energy. If an egg can be cooked that fast why not other foods? At that point, it was only a natural conclusion that microwave heating could raise the internal temperature of many foods far more rapidly than a conventional oven.
Dr. Spencer fashioned a metal box with an opening into which he fed microwave power. The energy entering the box was unable to escape, thereby creating a higher density electromagnetic field. When food was placed in the box and microwave energy fed in, the temperature of the food rose very rapidly. Dr. Spencer had...
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