Aspider hangs by a strand of silk at an eye level 20 cm in front of a plane mirror. you are behind the spider, 65 cm from the mirror. find the distance between your eye and the image of the spider in the mirror.

The image distance is equal to the object distance:

Distance between the spider and mirror = 20cm

So, the image is formed 20cm inside the mirror

Distance between the person and mirror = 65cm

Distance between the image and person = 65+20= 85cm

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