A microwave oven or simply microwave is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range. This induces polar molecules in the food to rotate and produce thermal energy in a process known as dielectric heating. Microwave ovens heat foods quickly and efficiently because excitation is fairly uniform in the outer 25–38 mm (1–1.5 inches) of a homogeneous, high-water-content food item.
A modern microwave oven (2022)
The cavity magnetron developed by John Randall and Harry Boot in 1940 at the University of Birmingham, England
Microwave ovens, several from the 1980s
Raytheon RadaRange aboard the NS Savannah nuclear-powered cargo ship, installed circa 1961
An oven is a tool which is used to expose materials to a hot environment. Ovens contain a hollow chamber and provide a means of heating the chamber in a controlled way. In use since antiquity, they have been used to accomplish a wide variety of tasks requiring controlled heating. Because they are used for a variety of purposes, there are many different types of ovens. These types differ depending on their intended purpose and based upon how they generate heat.
A double oven
A ceramic oven
Oven depicted in Jean-François Millet's painting, Woman Baking Bread (1854)
Ancient Greek portable oven, 17th century BC