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 scientific principle behind a microwave's door shielding?
The scientific principle is electromagnetic wave propagation and diffraction. Microwaves are electromagnetic waves with wavelengths around 12 cm. The metal mesh in the door has holes that are much smaller than this wavelength. When an electromagnetic wave encounters an aperture, it can only pass through if the aperture is significantly larger than the wavelength. Because the holes are smaller than the microwave wavelength, the waves are reflected or absorbed by the metal, rather than passing through. Visible light, with its very short wavelengths (nanometers), diffracts easily through these small holes.