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.
Is the metal grid in a microwave door solid or perforated?
The metal grid in a microwave door is perforated, meaning it has a pattern of small, uniformly sized holes. This perforation is not just for aesthetics; it's the key to its function. The grid is typically made of a conductive material, often steel or aluminum, and the density and size of the holes are critical. They are small enough to prevent microwave radiation from escaping but large enough to allow visible light to pass through, so you can monitor your food. The grid is usually integrated into a glass panel.