Which one of the following scenarios accurately describes a condition in which resonance can occur? a. a column of air has a height equal to 1⁄8 of the wavelength of the sound waves produced by a tuning fork vibrating over the column of air in an open pipe that's partially immersed in water. b. a person is holding a tuning fork on one end of a football field and another person is holding a separate tuning fork on the opposite end of the field. c. a pipe's length is equal to 1⁄2 of the wavelength of the sound waves produced by a tuning fork vibrating over one end of the pipe that's open to the air at both ends. d. a vibrating tuning fork is struck and begins to vibrate as the object used to strike it is placed away from the tuning fork.

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