What type of microscopy works by allowing only light waves that have reflected from or refracted though the sample to enter the lens system

dark-field microscopy

Explanation:

A darkfield microscope can be regarded as a brightfield microscope with a significant modification to condenser. There is an opaque disk, with a diameter of about 1cm placed in between the illuminator and condenser lens, the disk responsible for the blocking of most of the light from the illuminator, passing through the condenser to objective lens , which will then form hollow cone of light that has its focus on the specimen. Using a darkfield microscope the light that get to the objective is the only refracted or reflected light of structures in the specimen. And the image formed usually display a bright object with a dark background.

It should be noted that darkfield microscope is a type of microscopy works by allowing only light waves that have reflected from or refracted though the sample to enter the lens system.

double the distance = divide strength by 4

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