The solid metallic sphere is replaced with a hollow insulating shell of radius a. A charge Q is spread uniformly over the hollow spherical shell. What is the electric field strength inside the hollow shell at r

Zero

Explanation:

It is given that the charge is uniformly spread at the surface of hollow spherical shells.

There is no charge with in the hollo shell. hence, with zero charge the  electric field intensity is also zero.

Thus,

Magnitude of the electric field strength inside the hollow shell at r is zero

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

report!

explanation:

physics means: "the branch of science concerned with the nature and properties of matter and energy. the subject matter of physics, distinguished from that of chemistry and biology, includes mechanics, heat, light and other radiation, sound, electricity, magnetism, and the structure of atoms."