Communication Systems(11th And 12th > Physics ) Questions and answers for exam Preparation

11th And 12th > Physics

COMMUNICATION SYSTEMS MCQs

Total Questions : 30 | Page 1 of 3 pages

Question 1.

In which of the following remote sensing technique is not used

Forest density
Pollution
Wetland mapping
Medical treatment

Discuss Question

Answer: Option D. -> Medical treatment
:
D

Remote sensing is the technique to collect information about an object in respect of its size, colour, nature, location, temperature etc. without physically touching it. There are some areas or location which are inaccessible. So to explore these areas or locations, a technique known as remote sensing is used. Remote sensing is done through a satellite.

Question 2.

The bit rate for a signal, which has a sampling rate of 8 kHz and where 16 quantisation levels have been used is

32000 bits/sec
16000 bits/sec
64000 bits/sec
72000 bits/sec
If assertion is false but reason is true.

Discuss Question

Answer: Option A. -> 32000 bits/sec
:
A

If n is the number of bits per sample, then number of quantisation level = $2^{n}$
Since the number of quantisation level is 16
$\Rightarrow 2^{n} = 16 \Rightarrow$ n = 4
$∴$ bit rate = sampling rate $\times$ no.of bits per sample
= 8000 $\times$ 4 = 32,000 bits/sec

Question 3.

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : Television signals are received through sky-wave propagation.
Reason : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.

If both assertion and reason are true and the reason is the correct explanation of the assertion.
If both assertion and reason are true but reason is not the correct explanation of the assertion.
If assertion is true but reason is false.
If the assertion and reason both are false.
If assertion is false but reason is true.

Discuss Question

Answer: Option D. -> If the assertion and reason both are false.
:
D

TV signals (frequency greater than 30 MHz) cannot be propagated through sky wave propagation.

Above critical frequency, an electromagnetic wave penetratates the ionosphere and is not reflected by it.

Question 4.

Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion :The electromagnetic waves of shorter wavelength can travel longer distances on earth's surface than those of longer wavelengths.
Reason : Shorter the wavelength, the larger is the velocity of wave propagation.

Both assertion and reason are true and the reason is the correct explanation of the assertion.
Both assertion and reason are true but reason is not the correct explanation of the assertion.
Assertion is true but reason is false.
The assertion and reason both are false.
If assertion is false but reason is true.

Discuss Question

Answer: Option C. -> Assertion is true but reason is false.
:
C

The electromagnetic waves of shorter wavelength do not suffer much diffraction from the obstacles of earth's atmosphere so they can travel long distance.

Also, shorter the wavelength, shorter is the velocity of wave propagation.

Question 5.

If $f_{a}$ and $f_{f}$ represent the carrier wave frequencies for amplitude and frequency modulations respectively, then