What Form of Energy Are Microwaves?

Electromagnetic Radiation

• While some cooking devices are commonly called microwaves, the term "microwave" technically refers to a form of electromagnetic energy that travels in a vacuum at the speed of light. Like other forms of electromagnetic energy, bundles of energy called photons travel in a sine wave pattern and create an electromagnetic field perpendicular to their path. Forms of electromagnetic energy, including visible light, ultraviolet and infrared light, radiowaves, X-rays and gamma rays are classified by their wavelength, frequency and interaction with matter.

Energy of Microwaves

• Microwaves are found in the lower-energy end of the electromagnetic spectrum, between the energies of radiowaves and infrared light. The energy of microwaves is not a discrete frequency value but rather a range of frequencies. Microwave frequencies are found between 1 GHz and 300 GHz. The wavelength of microwaves fall into an approximate range of 1mm to 25um.

Microwave Oven History

• The microwave oven is a byproduct of a radar-related research project in 1946 by Dr. Percy Spencer, an engineer with Raytheon Corp. Later that year, the Raytheon Company filed a patent proposing the use of microwaves to cook food. In 1947, Raytheon introduced the world's first microwave oven and called it a "Radarange." By 1975 sales of microwave ovens outnumbered those of gas ranges.

How Microwaves Heat Food

• Due to the wavelength of microwaves, they are capable of interacting with food substances on a molecular level. As the microwave photons impart electromagnetic energy, the food molecules polarize and repolarize. This kinetic or moving energy causes friction, which finally dissipates as thermal energy, or heat. Some foods, due to their molecular composition, more efficiently absorb and transform microwaves into thermal energy, thereby causing certain foods to heat or cook faster than others.