Microwaves have frequencies ranging from about 1 billion cycles per second, or 1 gigahertz (GHz), up to about 300 gigahertz and wavelengths of about 30 centimeters (12 inches) to 1 millimeter (0. ...

That is half the wavelength of the microwaves that the oven produces. (Melty-bits shown in red.) Double that distance, and you’ll have the wavelength of the waves emitted by the microwave.