The distance between 2 corresponding (similar) parts of a wave (example- crest to crest) is its . *

-trough
-frequency
-amplitude
-wavelength

Wavelength        

Explanation:

A wave can be defined in terms of its frequency, wavelength, amplitude etc.

The distance between two corresponding parts of a wave, for example from crest to crest or trough to trough is called its wavelength.

It is represented by .

The relation between frequency, speed of a wave and its wavelength is given by :

So, the correct option is (4) "wavelength".

the answer for apex is the lowest

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