What Are Microwaves?

Microwaves are electromagnetic radiation that has a frequency higher than visible light but lower than radio waves. They are used in many places including homes, businesses, hospitals and military buildings.

Microwave radiation is generated by special vacuum tubes known as magnetrons, which were originally developed for radar use before and during World War II. American engineer Percy Spencer is generally credited with inventing the modern microwave oven after his first accidental experiment using a magnetron to cook popcorn and an egg.

In the microwave oven, a magnetron is mounted inside a metal cavity, which emits the microwaves. The microwaves bounce around inside the cavity, creating peaks (with lots of microwaves) and troughs (with few microwaves), much like waves in water. The rotating tray in your microwave is designed to ensure that all parts of the food are exposed to peaks so that they get heated.

Some foods absorb more microwaves than others. For example, different types of cooking oils and water-based liquids will heat up differently in the microwave. A fun experiment to try would be to put some water in a number of different containers and measure how quickly they heat up in the microwave.

Some studies have shown that the central nervous system is particularly sensitive to microwave radiation. The exact mechanisms are not yet fully understood, but they may involve oxidative and nitrosative stress, apoptosis, gene and protein expression, and energy metabolism. These changes can have negative impacts on learning and memory.