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.
Can I replace just the mesh on my microwave door?
Replacing just the mesh on a microwave door is generally not feasible or recommended for the average consumer. The mesh is typically integrated into the glass door assembly as a single unit. Attempting to replace it would require specialized tools and knowledge to ensure the new mesh is properly secured and sealed, maintaining the integrity of the microwave's shielding. It's usually more practical and safer to replace the entire door assembly if the mesh is damaged, or to service the microwave with a qualified technician.