The screen on the door of a microwave oven is designed to contain and prevent microwave energy from escaping. It is made up of a fine mesh or grid pattern that serves as a barrier for the microwaves. Here's why the microwave energy doesn't escape through the holes in the screen:
Wavelength: Microwave ovens operate at a frequency of around 2.45 gigahertz, which corresponds to a wavelength of approximately 12.2 centimeters. The holes in the screen are significantly smaller than the wavelength of the microwaves, making it difficult for the waves to pass through.
Faraday cage effect: The screen acts as a Faraday cage, named after the physicist Michael Faraday. A Faraday cage is an enclosure made of conductive material that blocks external electric fields. In this case, the screen is designed to reflect and absorb the microwaves, preventing their escape. The size and spacing of the holes in the screen are specifically designed to prevent microwave leakage.
Mesh density: The screen is made up of a fine mesh with closely spaced holes. The density of the mesh ensures that the majority of the microwave energy is reflected back into the oven cavity. Even if some energy manages to pass through one hole, it is highly likely to be reflected by the neighboring holes.
Oven construction: Apart from the screen on the door, microwave ovens are constructed with metal panels and a metal mesh lining the cavity walls. This construction further helps contain the microwaves within the oven, reducing the chances of leakage.
It's important to note that microwave ovens should be properly maintained and have a functioning door seal to ensure their safety and prevent any potential leakage. Manufacturers rigorously test and certify microwave ovens to meet safety standards and regulations regarding microwave radiation.