Question

Which of the following electromagnetic waves is used in telecommunication?

• A. radio waves
• B. visible radiations
• C. ultraviolet rays
• D. microwaves

Answer 1

The correct option is D

microwaves

Option D.

1. Microwave radiation has wavelengths between one meter and one millimeter, which correspond to frequencies between $300MHz$ and $300GHz$, respectively.
2. Prior to the development of fiber-optic transmission, carriers like AT&T Long Lines operated networks of microwave radio relay links that carried the majority of long-distance phone calls.
3. Starting in the early $1950s$, frequency-division multiplexing was utilized to transmit up to $5,400$ telephone channels on each microwave radio channel.
4. For the hop to the next site, which might be up to $70km$ away, as many as ten radio channels were multiplexed into one antenna.

Therefore, Microwaves are used in telecommunication. Hence, Option D is correct.