You must dim your high beams for oncoming vehicles by the time they are within 500 feet of your vehicle.

True

Explanation:

when oncoming vehicle driver is at a distance of 500 feet from you, then it is advisable to dim your high beam light so that it cannot blind oncoming vehicle driver. However, of the oncoming driver is at 200 to 300 ft then you must use low beam light so to pass the oncoming driver safely from your side. Hence the statement is true.

does anyone know or what?

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