Assertion and Reason Questions Chapter-15 Communication System
Assertion (A) and other labelled Reason (R). Select the correct answer to these
questions from the options as given below.
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true, but R is false.
D. A is false, but R is true.
1. Assertion (A): Amplitude modulation (AM) is widely used in commercial radio
broadcasting.
Reason (R): AM signals can travel long distances and are less
affected by noise.
2. Assertion (A): Frequency modulation (FM) is less susceptible to noise than
amplitude modulation (AM).
Reason (R): FM signals vary in amplitude, which enhances noise
immunity.
3. Assertion (A): The bandwidth of an FM signal is greater than that of an AM
signal.
Reason (R): FM modulates the frequency of the carrier wave,
leading to a wider range of frequencies.
4. Assertion (A): A modulated signal can be transmitted over long distances.
Reason (R): Modulation increases the frequency of the signal,
making it suitable for transmission.
5. Assertion (A): The carrier wave frequency must be higher than the message
signal frequency for effective modulation.
Reason (R): This prevents distortion of the original signal.
6. Assertion (A): Pulse modulation is less efficient than analog modulation
techniques.
Reason (R): Pulse modulation transmits more information in a given
bandwidth.
7. Assertion (A): The information capacity of a communication channel increases
with bandwidth.
Reason (R): Bandwidth determines the number of signals that can be
transmitted simultaneously.
8. Assertion (A): Noise in communication systems can be minimized using
modulation techniques.
Reason (R): Modulation shifts the signal frequency to reduce noise
interference.
9. Assertion (A): Analog signals can be represented by discrete values.
Reason (R): Discrete representation is essential for digital
communication.
10. Assertion (A): A demodulator is used to retrieve the original message signal
from a modulated carrier wave.
Reason (R): The demodulator performs the inverse operation of
modulation.
11. Assertion (A): The concept of multiplexing allows multiple signals to be
transmitted simultaneously.
Reason (R): Multiplexing combines signals into a single channel,
improving channel utilization.
12. Assertion (A): The modulation index determines the extent of modulation in
an AM signal.
Reason (R): A higher modulation index leads to better signal
quality.
13. Assertion (A): A radio receiver must be tuned to the frequency of the
incoming signal for effective reception.
Reason (R): Tuning ensures the receiver selects the desired signal
while rejecting others.
14. Assertion (A): A single-channel system is less complex than a multi-channel
system.
Reason (R): Fewer channels simplify the design and implementation
of the communication system.
15. Assertion (A): Satellite communication requires a line-of-sight path between
the transmitter and receiver.
Reason (R): Line-of-sight ensures minimal obstruction and maximum
signal strength.
16. Assertion (A): Digital communication systems are generally more secure than
analog systems.
Reason (R): Digital signals can be easily encrypted, enhancing
security.
17. Assertion (A): The Nyquist theorem is critical in determining the maximum
data rate for a communication channel.
Reason (R): It states that the maximum data rate is directly
proportional to the bandwidth of the channel.
18. Assertion (A): Light waves can be used for communication through optical
fibers.
Reason (R): Optical fibers use total internal reflection to
transmit light signals effectively.
19. Assertion (A): The Earth’s atmosphere can affect the transmission of radio
waves.
Reason (R): Atmospheric conditions such as temperature and
humidity can lead to signal attenuation.
20. Assertion (A): Communication systems require modulation to convert audio
signals into radio waves.
Reason (R): Modulation allows the audio signal to be effectively
transmitted over long distances.
21. Assertion (A): Baseband signals cannot be transmitted directly over long
distances.
Reason (R): Baseband signals are prone to distortion and
attenuation over long distances.
22. Assertion (A): Direct sequence spread spectrum (DSSS) is a method used to
increase the security of communication.
Reason (R): DSSS spreads the signal over a wider bandwidth, making
it difficult to intercept.
23. Assertion (A): A coherent receiver requires the presence of a carrier signal
for demodulation.
Reason (R): The carrier signal helps in restoring the original
signal during demodulation.
24. Assertion (A): The bandwidth of a communication channel can be increased
using modulation techniques.
Reason (R): Modulation shifts the frequencies of the signals to
utilize higher frequency ranges.
25. Assertion (A): Communication systems must be designed to minimize the
effects of multipath propagation.
Reason (R): Multipath propagation can lead to signal fading and
distortion.
26. Assertion (A): The modulation index of an FM signal determines its
bandwidth.
Reason (R): The bandwidth of FM is proportional to the maximum
frequency deviation.
27. Assertion (A): The use of antennas is crucial in both transmitting and
receiving communication signals.
Reason (R): Antennas convert electrical signals into
electromagnetic waves and vice versa.
28. Assertion (A): Optical communication systems are less prone to interference
than radio communication systems.
Reason (R): Optical signals operate in a different frequency
range, reducing the likelihood of interference.
29. Assertion (A): The signal-to-noise ratio (SNR) is a critical factor in
communication systems.
Reason (R): A higher SNR indicates better signal quality and lower
interference.
30. Assertion (A): Different types of modulation techniques are used depending
on the application.
Reason (R): Each modulation technique has its advantages and
limitations.
31. Assertion (A): The presence of a carrier wave is necessary for amplitude
modulation.
Reason (R): The carrier wave provides the frequency upon which the
audio signal is superimposed.
32. Assertion (A): Digital signals are more robust against noise compared to
analog signals.
Reason (R): Digital signals have discrete levels, which makes them
easier to distinguish from noise.
33. Assertion (A): Synchronous and asynchronous transmission are two methods of
data transfer in communication systems.
Reason (R): Synchronous transmission requires a clock signal for
data timing, while asynchronous does not.
34. Assertion (A): Frequency modulation (FM) signals have a larger bandwidth
than AM signals.
Reason (R): The frequency deviation in FM is greater than the
amplitude variation in AM.
35. Assertion (A): Communication satellites are primarily used for global
telecommunications.
Reason (R): They provide a line-of-sight path for signal
transmission across long distances.
36. Assertion (A): The Doppler effect is significant in mobile communication.
Reason (R): The relative motion between transmitter and receiver
causes frequency shifts.
37. Assertion (A): Modulation is not necessary for transmitting digital signals.
Reason (R): Digital signals can be transmitted directly without
any modification.
38. Assertion (A): Spread spectrum techniques enhance the security of
communication.
Reason (R): They reduce the chance of interception by spreading
the signal across multiple frequencies.
39. Assertion (A): The use of digital signal processors (DSPs) is common in
modern communication systems.
Reason (R): DSPs are efficient in processing and manipulating
digital signals for communication.
40. Assertion (A): The amplitude of a modulated signal does not vary in
amplitude modulation (AM).
Reason (R): The amplitude varies in accordance with the message
signal.
41. Assertion (A): The noise figure of a communication system indicates its
performance.
Reason (R): A lower noise figure means better signal quality and
less noise interference.
42. Assertion (A): Line-of-sight communication is essential for microwave
transmission.
Reason (R): Microwave signals are easily blocked by obstacles.
43. Assertion (A): Digital communication systems are inherently more efficient
than analog systems.
Reason (R): Digital systems allow for error correction and
compression techniques.
44. Assertion (A): The frequency response of a communication system is important
for its design.
Reason (R): It determines how the system responds to different
frequencies of input signals.
45. Assertion (A): The use of error detection and correction methods is crucial
in communication systems.
Reason (R): They ensure the accuracy of data transmission over
noisy channels.
46. Assertion (A): Analog signals can represent a continuous range of values.
Reason (R): They are not limited to discrete levels as digital
signals are.
47. Assertion (A): Communication systems using fiber optics have higher data
transmission capacity than traditional systems.
Reason (R): Fiber optics utilize light signals, which can carry
more information over longer distances.
48. Assertion (A): Modulation is necessary for enabling multiplexing in
communication systems.
Reason (R): Modulation allows multiple signals to share the same
communication medium.
49. Assertion (A): The performance of a communication system can be measured by
its bandwidth and signal-to-noise ratio (SNR).
Reason (R): Both parameters are crucial for determining data
transfer rates and signal clarity.
50. Assertion (A): Communication systems are evolving to incorporate advanced
technologies such as 5G and IoT.
Reason (R): These technologies require higher data rates and lower
latency for effective operation.