on tube acts like the "chattering ball" inside "a whistle (7:54-60)." The strip modifies the electrons' vibrations such that they primarily produce microwaves.
Magnetrons may employ ferrite magnets. For most domestic applications, units rated at 600 watts or 1 kilowatt are generally sufficient. The power which is delivered by microwave energy depends on its frequency. The microwaves produced by most magnetrons has a frequency of 2450 megahertz. The 2450 wavelength magnetrons are not only compact, they also provide an optimum energy distribution within various oven loads (2:401-402).
Once a magnetron shapes electromagnetic energy into microwaves, the energy must then be reflected onto the food. Typically, the microwave signal is channelled down a waveguide. Magnetrons may only deliver half their energy to the actual oven cavity (5:26). In addition, the ovens may also produce hot-spots and cold-spots within loads. Hence, microwaves moving down a waveguide may be re-radiated off the blades of a moving fan. By producing continuously changing conditions within the oven cavity, such fans more evenly distribute the magnetron's energy. Alternatively, ovens without fans may employ rotating platters. These ensure that all food at a given radius and height receives the same total microwave exposure (8:474-476).
While microwave ovens have been around for several decades, only recently have researchers begun to understand precisely how they work. Dielectric, or polar, materials have one positive end a
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