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. ...

The screen is designed with holes that are the perfect size to keep microwaves, which have a wavelength of 4.8 inches, inside of the device while it's running.