Microwave doors block radiation using a metal mesh with holes smaller than the wavelength of microwaves, but larger than visible light waves.
The metal mesh in a microwave door acts as a Faraday cage for microwave radiation. Microwaves have a relatively long wavelength, typically around 12 cm. The holes in the mesh are significantly smaller than this wavelength, preventing the microwaves from passing through and escaping the oven. However, visible light has a much shorter wavelength, on the order of nanometers, allowing it to easily pass through the same holes, which is why you can see inside the microwave.
While microwave doors are designed to contain radiation, it's always wise to ensure your appliance is in good condition and not damaged.
What materials are used for microwave radiation shielding in doors?
Microwave radiation shielding in doors is primarily achieved using a conductive metal mesh, typically made of aluminum or stainless steel. This mesh is integrated into the glass door panel. The metal itself reflects microwave energy, and the pattern of holes is critical. The holes are designed to be smaller than the wavelength of the microwaves (about 12 cm), preventing them from passing through. The conductive nature of the metal allows any induced currents from the microwaves to flow and cancel out the field, effectively trapping the radiation inside the oven.