Which of the following statements are true concerning the creation of magnetic fields? check all that apply. check all that apply. a distribution of electric charges at rest creates a magnetic field at all points in the surrounding region. a permanent magnet creates a magnetic field at all points in the surrounding region. an electric current in a conductor creates a magnetic field at all points in the surrounding region. a moving electric charge creates a magnetic field at all points in the surrounding region. a single stationary electric charge creates a magnetic field at all points in the surrounding region.

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electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

snell's law

refractve index = sin incidence / sin refraction