What variables must be known to determine the observed frequency of a wave?

The frequency, 'f', of a wave is given by the speed, 'v' of the wave and the wavelength, λ, of the wave

f = v/λ

The frequency, 'f', of a wave is also given by the inverse of the period, 'T', of the wave which is the time it takes the wave to complete an oscillation or a cycle

f 1/T

Therefore, the variables to be known to determine the frequency of a wave includes either, the velocity and the wavelength of the wave or the period of oscillation (the wave cycle) of the wave

Explanation:

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

total distance/total time

(85 + 82)/(5+3)

167/8

20 just over