Consider a solid cylinder of length 1 and radius a. assume the length 1 to be very large, such that all edge effects of the cylinder can be ignored. the cylinder has surface charge density o and volume charge density p(r) given by: 1 kr2 for r a. i) determine the electric field e(r) and potential v(r) for r a. ii) a second hollow cylinder of equal length 1, radius b such that b> a and surface charge density o is placed around the first cylinder. determine the effect on the electric fields in the regions: p

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

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.