Characteristics of Microwaves

The electromagnetic (EM) radiation spectrum is essentially an arrangement of the various forms of electromagnetic radiation by the order of their frequencies. At the low-frequency end of the spectrum is radio-wave energy. At the high end are gamma rays. Microwaves, infrared, visible light, ultraviolet and X-rays are in the middle of the spectrum. EM radiation with wavelengths between 1 GHz to 300 GHz falls into the microwave category.

To make high-frequency microwaves suitable for heating and cooking food, the microwave oven needs a supply of high-voltage electric power. Household electricity in the U.S. is typically delivered at only 120 volts. Inside the oven, a step-up transformer increases the voltage to between 3,000 and 5,000 volts. The magnetron transforms the high-voltage electricity into electromagnetic radiation in the form of microwaves.

Microwaves are composed of bundles of energy that travel through a vacuum in a sine-wave form. Ultimately, EM radiation is classified by its ability to interact with matter. Microwaves interact with most food substances at the molecular level. Like visible light, microwaves may be reflected, refracted and attenuated by certain substances.

Unlike conventional stoves, microwave ovens do not have heating elements. Inside your microwave oven, electrical energy is transformed into EM energy in the magnetron. When the microwave photons interact with food, food molecules are physically agitated, transforming the EM energy into kinetic energy, or energy of movement. Movement of the food molecules is hindered by friction, which finally transforms the kinetic energy into thermal energy, or heat.

While all microwave ovens share common basic features, higher-end models may have dual cookimg modalities such as browning elements and convection capability. Many units have rotating turntables for even cooking and variable power levels for slow cooking and thawing.