Using a wavelength laser, you form the diffraction pattern of a wide slit on a screen. you measure on the screen that the dark fringe is away from the center of the central maximum. how far is the screen located from the slit?

y = λ   L/ a

Explanation:

The diffraction pattern of a single slit is side for the case of destructive interference by

     a sin  θ = m λ

Where a is the width of the slit, lm the wavelength and m an integer

In general the screen is much larger than the width of the spectrum, so the sine can approach the tangent

       sin  θ = tan θ = y / L

Substituting remains

       a y / L = m λ  

       y = m λ  L /a

For the first dark strip m = 1

      y = λ   L/ a

d eras and periods

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