12. which of the following accurately describes semiconductor diodes?
a. point-contact diodes are more likely to be used as rectifiers than junction diodes.
b. unlike junction diodes, point-contact diodes are enclosed in a suitable casing and have terminals for connecting them to a circuit.
c. unlike point-contact diodes, junction diodes utilize a point of metal wire in contact with a single wafer of p-type or n-type material.
d. junction diodes are preferred over point-contact diodes for most purposes.

Answer;

D. Junction diodes are preferred over point-contact diodes for most purposes.

Junction diodes are preferred over point-contact diodes for most purposes; accurately describes semiconductor diodes.

Explanation;

-Semiconductor diodes are specialized electronic components with two electrodes called the anode and the cathode, that are made with semiconductor materials such as silicon, germanium, or selenium.

-Point contact diode is formed by touching a metallic wire with an N-type semiconductor to form a small area of contact.

-A p-n junction diode is two-terminal or two-electrode semiconductor device, which allows the electric current in only one direction while blocks the electric current in opposite or reverse direction. Junction diodes are preferred over point-contact diodes for most purposes.

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