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Clara Chung
- 304
- 14
A metal piece has no E field inside too. Why must the microwave use a metal mesh with hollow spaces to block radiation? They can simply use a metal piece just like the interior part of the box.
Clara Chung said:Why must the microwave use a metal mesh with hollow spaces to block radiation? They can simply use a metal piece just like the interior part of the box
exactlyruss_watters said:So you can see through the window.
Note that it is not a mesh that is used but it is a sheet of perforated metal. That is easier to clean and more conductive. If the dimensions of a hole are all less than about one tenth of a wavelength then microwave radiation cannot radiate through the hole. You can see inside through the perforations because light has a much shorter wavelength than microwaves. The outside of the perforated sheet is painted black to make it easier for you to see inside without problems from external lighting.Clara Chung said:Why must the microwave use a metal mesh with hollow spaces to block radiation?
Baluncore said:Note that it is not a mesh that is used but it is a sheet of perforated metal. That is easier to clean and more conductive. If the dimensions of a hole are all less than about one tenth of a wavelength then microwave radiation cannot radiate through the hole. You can see inside through the perforations because light has a much shorter wavelength than microwaves. The outside of the perforated sheet is painted black to make it easier for you to see inside without problems from external lighting.
The 2.45GHz microwave radiation used has a wavelength of 12 cm so you might ask why they do not use 12 mm holes? The answer is that, from a distance, you can see through many small holes better than through a few large ones.
A Faraday cage is designed to protect the inside contents from external electromagnetic fields. In order for this to be effective, the cage must be completely enclosed, including the top, bottom, and all sides. If the cage were not hollow, there would be no way for the electromagnetic fields to be blocked from entering the inside of the cage.
While a Faraday cage can be made out of a variety of materials, it is important that the material used is conductive. This allows the electromagnetic fields to be redirected and absorbed by the cage, rather than passing through it and affecting the contents inside. Some common materials used for Faraday cages include copper, aluminum, and steel.
A Faraday cage works by utilizing the principle of electrical conductivity. When an external electromagnetic field encounters the metal surface of the cage, it induces an equal and opposite electrical charge on the surface. This charge creates an electric current that cancels out the external field, effectively shielding the contents inside the cage from its effects.
For most individuals, a Faraday cage is not necessary for everyday use. However, it can be useful in certain situations, such as protecting sensitive electronic equipment from electromagnetic interference or in the event of a lightning strike. Some people also use Faraday cages to block out cell phone signals or to protect against identity theft.
No, a Faraday cage is not able to protect against all types of electromagnetic radiation. It is most effective against low-frequency electromagnetic fields, such as those from power lines or lightning strikes. It is not as effective against high-frequency radiation, such as x-rays or gamma rays, as these have much smaller wavelengths that can pass through the openings of a Faraday cage.