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 is the typical size of holes in a microwave door mesh?
The holes in a microwave door mesh are precisely engineered to be smaller than the wavelength of microwave radiation, which is around 12 centimeters (about 4.7 inches). Specifically, the holes are typically around 1-2 millimeters in diameter. This size difference is crucial; it allows visible light, with its much shorter wavelengths, to pass through freely, enabling you to see the food cooking, while effectively blocking the escape of longer microwave waves. The mesh itself is usually made of a conductive metal, like aluminum or steel, which further helps in reflecting and containing the microwaves.