Question

The waves used in telecommunication are-
(A). Infrared
(B). Ultraviolet
(C). Microwaves
(D. Cosmic waves

Answer 1

- Hint: The entire distribution of electromagnetic radiation by frequency or wavelength, is known as the electromagnetic spectrum. While all electromagnetic waves travel in a vacuum at the speed of light, it is obvious that they travel at a variety of frequencies, wavelengths and photon energies.

Complete step-by-step answer:
The electromagnetic spectrum consists of many subranges, commonly called portions of visible light or ultraviolet radiation, and is the span of all electromagnetic radiation. Similar parts have different names based on individual variations in wave emission, transmission and absorption and on their various functional applications.
Microwaves are electromagnetic radiation with wavelengths between 1 m and 1 mm and frequencies ranging from 300 MHz to 300 GHz. Microwaves travel by sight line; as opposed to the lower frequency radio waves they do not scatter over hills, follow the surface of the earth as ground waves, or reflection from the ionosphere, and the terrestrial communications of microwaves are limited to approximately 40 miles (64 km) by the visual horizon. These are absorbed by gases at the high end of the band and restrict practical distances of communication to around one kilometre.
Modern technology uses microwave systems, such as point-to – point communication links, cellular networks, microwave radio relay networks, radar, satellite communication, and spacecraft.
Hence, it’s clear that option C is the correct option.

Note: All the radio waves (e.g., commercial radio and television, microwaves, radar), infrared , visible light, ultraviolet radiation, x-ray, and gamma rays are part of the total electromagnetic spectrum from the lowest to the highest frequency (longest to lowest wavelength). Almost all electromagnetic radiation frequencies and wavelengths can be used for spectroscopy.