Electromagnetic Waves Test - 3

Since both electric and magnetic fields oscillates perpendicular to direction of propagation of em-wave, it is transverse in nature.

The waves used in telecommunication are microwaves.

Electromagnetic waves are waves that, as in space, can propagate in a vacuum. This is because they are not in real material vibrations; they are electrical and magnetic field variations. Examples are radio waves, microwaves, infrared, light-visible, ultraviolet, x-ray, and gamma rays include electromagnetic waves. The lowest energy, frequency, and wavelength are radio waves. The maximum intensity and frequency with the lowest wavelength are gamma rays. Examples of telecommunications products include television, radio, fiber optics, satellites, and the internet.

Microwaves are electromagnetic radiation that finds applications in communications, radar, and cooking. The frequencies of microwaves range from \(1 {~GHz}\) to \(300 {~GHz}\).

Thus in telecommunication, microwaves are used.

Hence, the correct option is (C).

Maxwell showed that Ampere's circuital law is logically inconsistent. He considered a parallel plate capacitor being charged be a battery. He showed inconsistency of the law in the regions outside the plates of capacitor and just between the plates. To resolve this inconsistency displacement current was introduced by Maxwell.

A time varying magnetic field is a source of changing electric field. And a time varying electric field is a source of changing magnetic field. These variations in electric field and magnetic fields occur in mutually perpendicular directions and have wave like properties. Maxwell was thus led to the idea that a wave of electric and magnetic fields both varying with  space and time should exist, one providing the source of another. Such a wave is called electromagnetic wave.

This charge produces an oscillating electric field in its neighbourhood. This field in turn, produces an oscillating magnetic field in its neighbourhood. The process continues as both the fields acts as source of each other. Hence an em wave originates from the oscillating charge.
Note: The frequency of em wave is equal to frequency of oscillating charge.