Question

In space communication, the information can be passed from one place to another at a distance of 100 km in:
A) $1\sec $
B) $0.5\sec $
C) $0.0033\sec $
D) $0.00033\sec $

Answer 1

Hint: To solve this problem, we have to compute the mechanism in which the communication happens in space and correspondingly, the speed of the channel used in the communication of the information.

Complete step by step solution:
Let us understand the mechanism of information transfer that happens across space.
The space communication consists of two major components: Transmitter and Receiver.
A transmitter encodes the information signal and modulates it to a high-wavelength radiation in the form of radio-waves or microwaves which are emitted.
The receiver catches this radiation and demodulates it and then, the message signal is received at the other end.
Thus, we see that the radio-waves or microwaves are used for space communication purposes.
Radio wave is the part of the electromagnetic radiation spectrum whose wavelength is longer than infrared light. The radio waves have a wide range of frequencies up to $30GHz - 300GHz$. Hence, its corresponding wavelength ranges from as low as 1 mm to almost $10,000km$. This huge range of wavelength is employed for communications over very large distances across ground-to-ground or ground-to-air.
Since the radio-waves belong to the spectrum of electromagnetic radiation, the spectrum of electromagnetic radiation have a constant velocity and the value of velocity is given by:
$c = 3 \times {10^8}m{s^{ - 1}}$
Now, the distance to be travelled by the radiowaves is equal to –
$\Rightarrow d = 100km = 100 \times {10^3}m$
The time taken to travel is obtained by dividing the distance to be travelled by the speed of light.
$\Rightarrow t = \dfrac{d}{s} = \dfrac{{100 \times {{10}^3}}}{{3 \times {{10}^8}}} = 33.33 \times {10^{ - 5}}\sec $
$\therefore t = 0.00033\sec $

Hence, the correct option is Option D.

Note: Here, we have to consider the fact that the velocity of light remains constant in vacuum or any other medium. This gives us the relation that the distance covered is directly proportional to the time taken. This means that if the distances are too long, the time taken for the information signal to reach will be very large.