Microwaves: A Hot Commodity for More than Just Hot Food

By Anastasia Faddis

I was recently in the kitchen heating up some leftovers in my microwave when I thought of a medical article I had seen that used microwaves to treat cancer. Microwaves, at least as I knew them, were simply a great kitchen appliance that could turn yesterday’s pizza into a delicious late-night snack. But as it turns out, microwaves have a wide range of applications, from radar technology to minimally invasive surgery… and of course, for food.

Microwaves are a type of electromagnetic radiation. They have wavelengths ranging from 1 millimeter to 1 meter and are between infrared light and radio waves on the electromagnetic spectrum. Microwaves interact with materials in specific ways, passing through materials like glass and plastic, but being absorbed by water, sugars, and fat. These interactions allow for the phenomenon of dielectric heating, in which microwaves interact with polar molecules (which contain a slightly positive end and a slightly negative end), creating a magnetic field that oscillates. The oscillation of this magnetic field causes polar molecules, such as water, to begin rotating back and forth. This rotation creates friction between the molecules, which is converted to heat energy. The concept of dielectric heating is the basis for microwave ovens.

While microwave ovens are the first thing that comes to mind when I think of microwave radiation, it was initially used for a very different purpose. Microwaves were first utilized in radar technology to detect enemy ships and aircraft during World War II. Microwaves could be bounced off faraway objects, such as ships and aircraft, and the returning signal would be detected with directional antennas, allowing for the presence and location of those objects to be determined. This type of radar became highly important for military purposes but has since been used for a variety of applications. Microwaves are now used for motion detectors, radar guns for the enforcement of speed limits, air traffic control, and weather radar.

In addition to using microwave radiation for the detection of objects, microwaves can also be used for the transmission of information. Microwaves are now commonly used for point-to-point communication, allowing for narrower beams to be sent between smaller antennas. These beams are also more tightly focused than radio waves, meaning they interfere with each other less. While microwave signals are limited to line of sight, meaning no major disturbances can be in their path, their higher frequency allows for more information to be transmitted. Because of their large capacity for information, microwaves are becoming more and more important for modern communication systems, providing us with cellular networks, wireless internet, and TV broadcasting.

Microwaves are not only used for the detection of objects and the heating of food, but they can also be used for the detection and heating of abnormal tissues. Microwaves have grown increasingly important within the medical field. Microwave imaging has been researched as an alternative to X-rays, which use ionizing radiation that can cause cancer. Microwave imaging relies on knowledge of the difference in conductivity of malignant and healthy tissues from their differing water contents and dielectric properties. This allows the microwave radiation to be absorbed by these tissues differently, allowing the types of tissue to be imaged. Microwaves have also been researched as a treatment for cancer cells. Microwaves are used to destroy cancer cells by heating them until the structure and proteins of those cells are destroyed. Since tumor cells have a higher water content than healthy cells, this method can induce rapid heating within tumor cells while making little difference in healthy cells.

Given the broad applications of microwaves and their use in our everyday lives, it is a shame they are primarily known for just their heating capabilities. From providing us with radar to predict the weather, to cellular networks for communication, and even for the treatment of cancer, microwaves are able to do it all. The next time you go to reheat some day-old pizza in your microwave oven, don’t forget the importance of microwaves in all aspects of your life.