Microwaves :: essays research papers

You might remember the heroic role that newly-invented radar played in the Second World War. People hailed it then as "Our Miracle Ally". But even in its earliest years, as it was helping win the war, radar proved to be more than an expert enemy locator. Radar technicians, doodling away in their idle moments, found that they could focus a radar beam on a marshmallow and toast it. They also popped popcorn with it. Such was the beginning of microwave cooking. The very same energy that warned the British of the German Luftwaffe invasion and that policemen employ to pinch speeding motorists, is what many of us now have in our kitchens. It's the same as what carries long distance phone calls and cablevision. Hitler's army had its own version of radar, using radio waves. But the trouble with radio waves is that their long wavelength requires a large, cumbersome antenna to focus them into a narrow radar beam. The British showed that microwaves, with their short wavelength, could be focussed ina narrow beam with an antenna many times smaller. This enabled them to make more effective use of radar since an antenna could be carried on aircraft, ships and mobile ground stations. This characteristic of microwaves, the efficiency with which they are concentrated in a narrow beam, is one reason why they can be used in cooking. You can produce a high-powered microwave beam in a small oven, but you can't do the same with radio waves, which are simply too long. Microwaves and their Use The idea of cooking with radiation may seem like a fairly new one, but in fact it reaches back thousands of years. Ever since mastering fire, man has cooked with infrared radiation, a close kin of the microwave. Infrared rays are what give you that warm glow when you put your hand near a room radiator or a hotplate or a campfire. Infrared rays, flowing from the sun and striking the atmosphere, make the Earth warm and habitable. In a conventional gas or electric oven, infrared waves pour off the hot elements or burners and are converted to heat when they strike air inside and the food. Microwaves and infrared rays are related in that both are forms of electromagnetic energy. Both consist of electric and magnetic fields that rise and fall like waves on an ocean. Silently, invisibly and at the speed of light, they travel through space and matter. There are many forms of electromagnetic energy (see diagram). Ordinary light from the sun is one, and the only one you can actually see. X-rays are another. Each kind, moving at a separate wavelength, has a unique effect on any matter it