Introduction
This proposal is about the physics of microwave oven. This includes the interaction of microwaves with metals and the generation of microwaves in magnetrons. The reason for choosing a microwave oven is because they are used common places like in homes and restaurants for warming food.
A microwave is a wave that belongs the class of electromagnetic waves. They have frequencies ranging from 300 MHz to 300GHz and wavelengths ranging from 1 m to 1mm. (Bradshaw, Van & Swardt, 201)
Physics of the Microwave
A typical microwave oven consists of the magnetron, fan, power supply, waveguide, turntable and a base plate. The microwaves are produced by the magnetron that is feed to the cooking chamber through a waveguide. The common microwaves use a rotating turntable to cook food, but a few uses a rotating reflector that acts as a stirrer ("Microscopic Microwave", 2)
Microwaves and Metals
The microwaves that are incident on the metal walls of the oven behave like the visible light that hits a mirror. These waves are effectively absorbed because the electric fields are interact strongly with the free electrons of the nearby metal. The excited electrons then radiate the electromagnetic waves having a similar frequency and in phase making them be perfectly reflected.
Production of Microwaves in magnetrons
Most of the microwave ovens use magnetrons. A cylindrical cathode which is on axis with the anode and it is some millimeters apart. The anode has some inside cavities that resonate at frequencies of 2.45 GHz. Several KVs of voltage is applied to the electrodes with the magnetic field parallel to the axis, and the two are perpendicular to each other. The electrodes are ejected from the cathode and follow the cycloidal paths due to the magnetic fields. The strong magnetic fields allow the electrons to reach the anode inform of a rotating space charge. The resonating cavities interact with these electrons by decelerating or accelerating them. The effect is the creation of electron bunches that goes around the cathode as microwaves (Parker, Kelly & Volmer, 74)
Work Cited
Parker, Kerry, and Michael Vollmer. "Bad food and good physics - the development of domestic microwave cookery." Physics Education 39.1 (2004): 82.
Bradshaw, S. M., E. J. Van Wyk, and J. B. De Swardt. "Microwave heating principles and the application to the regeneration of granular activated carbon." Journal of the South African Institute of Mining and Metallurgy (South Africa) 98.4 (1998): 201-210.
"Microscopic Microwave Oven [News Brief]". IEEE Spectr. 45.1 (2008): 20-20. Web.
