Microwave Ovens
Microwave ovens are kitchen appliances that use microwave radiation to heat food quickly and efficiently, making them a popular choice in many households since the 1960s. The technology behind microwave cooking stems from the theoretical work of James Clerk Maxwell, who formulated the electromagnetic theory in the late 19th century. This theory was later validated by Heinrich Hertz's experiments, establishing the foundation for understanding electromagnetic waves, which include the microwaves used in cooking.
The accidental discovery of using microwaves for heating food was made in 1945 by engineer Percy Spencer, who noticed a chocolate bar in his pocket melting while he was working with radar technology. This led to the development of the first microwave oven, which was designed to create a high-density electromagnetic field for efficient heating. Microwave ovens work by causing polarized molecules in food to oscillate, generating heat through friction. Despite their convenience, research is ongoing to improve microwave cooking, specifically to address issues like uneven heating, which can lead to poorly cooked food. Overall, microwave ovens exemplify how abstract mathematical concepts can translate into practical applications that enhance daily life.
Microwave Ovens
SUMMARY: An accidental discovery led to the use of microwave ovens for cooking, a process that continues to be studied.
In 1873, James Clerk Maxwell, using only mathematical considerations, formulated the electromagnetic theory. Maxwell’s equations are fundamental to physics and engineering and describe light as a form of electric and magnetic energy. Fifteen years later, experiments carried out by Heinrich Hertz validated Maxwell’s theory of electromagnetic waves. This development is a good example of mathematics as a creative medium for the development of science and technology. One of the technological products of Maxwell’s theory can be found in most homes in developed countries. Domestic microwave ovens have become increasingly popular since the 1960s, as the device offers a quick method for heating food compared to conventional heating methods. The discovery of electromagnetic waves by Maxwell shows how pure abstract mathematics can generate new technologies. Applied mathematicians also learn new mathematics from problems motivated by this type of application.
Electromagnetic Waves
Electromagnetic waves are a form of radiation represented by their frequency and wavelength. Frequency is the number of cycles that occur in a second and is measured in Hertz (Hz). Wavelength is the measure of the distance over which the wave’s shape repeats (λ). The electromagnetic spectrum consists of all possible frequencies and wavelengths of electromagnetic radiation, for example, radio waves, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays. Microwaves are electromagnetic waves with high frequencies (between 300 MHz and 300 GHz and short wavelengths (from as long as one meter to as short as one millimeter). Besides microwave ovens, practical applications of microwave technology can be found in cellular telephones, radar, satellites, and medical systems.
Discovery
The discovery that microwaves could be used for heating food is one of the accidental cases in the history of science. It occurred in 1945 when Percy Spencer, an American self-taught engineer, was working with microwaves in a radar system and a peanut chocolate bar that was in his pocket started to melt. In the same year, after some experiments with popcorn and eggs, Spencer created the microwave oven. It consisted of a metal box with a high-density electromagnetic field to heat food quickly and efficiently. Twenty years later, microwave ovens were adapted for domestic use as the typical consumer microwave ovens that are known today.
How it Works
The physical and operating principles of microwave ovens are quite simple. Most foods are composed of polarized molecules that are bound together in different ways. When microwave radiation is exposed to food, the molecules within the food are forced to align themselves with a rapidly changing alternating electrical field. Charged molecules oscillate and gain thermal energy via friction. Therefore, microwave radiation can heat food when the radiation is absorbed. This process is dependent on the time of radiation exposition, type of food, and the way the radiation is distributed (scattered, reflected, or transmitted).
In the early twenty-first century, mathematicians are working in universities and industries where interesting problems can be solved using a mathematical approach. Industrial mathematicians at the University of Bath have been working on the microwave cooking process.
A problem with this process is that it can result in localized points inside a food where the radiant electromagnetic field is relatively weak—the temperature in this point may be lower—and the food will be poorly cooked. Theoretically, it is possible using a combination of both analytical and numerical calculation to create a three-dimensional field simulation of this process.
Through a mathematical simulation, an averaged electromagnetic field can be calculated, and it will be possible to determine how it penetrated a moist foodstuff. This example from applied mathematics shows us how mathematics can be used to help us create and enjoy the benefits of technology.
Bibliography
Budd, Chris. “Confessions of an Industrial Mathematician.” http://www.math.leidenuniv.nl/~naw/serie5/deel09/jun2008/budd.pdf.
Gallawa, J. Carlton “A Brief History of the Microwave Oven.” Southwest Museum of Engineering, Communications and Computation. http://www.smecc.org/microwave‗oven.htm.
University of Colorado. “How Microwaves and Microwave Ovens Work.” Physics 2000, Einstein’s Legacy. http://www.colorado.edu/physics/2000/microwaves.