JEE Physics Communication System MCQs Set 10

Download JEE MCQs for JEE Physics: Communication System

Review structured MCQ sets for JEE Physics Communication System. Built according to official JEE guidelines, these downloadable questions support daily revision and core concept reinforcement.

Chapter-wise Objective Questions: Communication System

Access the complete set of multiple-choice questions for Communication System below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official JEE textbooks.

Multiple Choice Questions

Question 1: If the output of the information source is a non-electrical signal like a voice signal, a ___A___ converts it to ___B___ form before giving it as an input to the ___C___. Here A, B and C refer to
(a) receiver, electrical, channel
(b) channel, magnetic, transducer
(c) transducer, electrical, channel
(d) transducer, electrical, transmitter
Show Answer & Explanation

Answer: (d) transducer, electrical, transmitter

Explanation:
1. A transducer converts the voice to an electrical signal which is fed to the transmitter.

Teacher's Note:
1. Recall the basic fact.

Question 2: A transmitter radiates 10 kW of power with the carrier unmodulated and 11.8 kW with the carrier sinusoidally modulated. The modulation factor is
(a) 56%
(b) 60%
(c) 72%
(d) 84%
Show Answer & Explanation

Answer: (b) 60%

Explanation:
1. P_t = P_c(1 + m²/2), so 1.18 = 1 + m²/2.
2. m² = 0.36 and m = 0.6 = 60%.

Teacher's Note:
1. Recall the basic fact.

Question 3: Ground wave propagation is possible for
(a) low radio frequency over a short range
(b) high radio frequency over a short range
(c) high radio frequency over a long range
(d) low radio frequency over a long range
Show Answer & Explanation

Answer: (a) low radio frequency over a short range

Explanation:
1. Ground waves are attenuated rapidly as frequency rises, so they serve low frequencies over short ranges.

Teacher's Note:
1. Recall the basic fact.

Question 4: Optical fibre are used for long distance communication because
(a) it amplifies signals to be transmitted
(b) it transfers signals faster than electrical cables
(c) it pre-emphasises weak signals
(d) it provides little attenuation as compared to electrical cable for light propagation
Show Answer & Explanation

Answer: (d) it provides little attenuation as compared to electrical cable for light propagation

Explanation:
1. Optical fibres have very low attenuation.

Teacher's Note:
1. Recall the basic fact.

Question 5: Telephony is an example of ________ mode of communication.
(a) point-to-point
(b) broadcast
(c) both (a) and (b)
(d) None of these
Show Answer & Explanation

Answer: (a) point-to-point

Explanation:
1. A telephone call links one transmitter and one receiver.

Teacher's Note:
1. Recall the basic fact.

Question 6: During the process of transmission and reception the signal gets deteriorated due to
(a) noise introduced in the system
(b) distortion in the system
(c) both (a) and (b)
(d) neither (a) nor (b)
Show Answer & Explanation

Answer: (c) both (a) and (b)

Explanation:
1. Both noise and distortion degrade the signal.

Teacher's Note:
1. Recall the basic fact.

Question 7: Pre-emphasis in FM system is done to
(a) compress modulating signal
(b) expand modulating signal
(c) amplify lower frequency component of the modulating signal
(d) amplify higher frequency component of the modulating signal
Show Answer & Explanation

Answer: (d) amplify higher frequency component of the modulating signal

Explanation:
1. High audio frequencies are boosted before transmission to improve signal-to-noise ratio.

Teacher's Note:
1. Recall the basic fact.

Question 8: The AM wave is equivalent to the summation of
(a) two sinusoidal waves
(b) three sinusoidal waves
(c) four sinusoidal waves
(d) None of these
Show Answer & Explanation

Answer: (b) three sinusoidal waves

Explanation:
1. An AM wave contains the carrier and two side bands: three sinusoids.

Teacher's Note:
1. Recall the basic fact.

Question 9: In frequency modulation
(a) the amplitude of modulated wave varies as frequency of carrier wave
(b) the frequency of modulated wave varies as amplitude of modulating wave
(c) the frequency of modulated wave varies as frequency of modulating wave
(d) the frequency of modulated wave varies as frequency of carrier wave
Show Answer & Explanation

Answer: (b) the frequency of modulated wave varies as amplitude of modulating wave

Explanation:
1. In FM the instantaneous carrier frequency varies with the amplitude of the modulating signal.

Teacher's Note:
1. Recall the basic fact.

Question 10: Depth of modulation in terms of Emax and Emin is
(a) \( m_a=E_{max}+E_{min}/E_{max} \)
(b) \( m_a=E_{max}-E_{min}/E_{max} \)
(c) \( m_a=\frac{E_{max}-E_{min}}{E_{max}+E_{min}} \)
(d) \( m_a=\frac{E_{max}+E_{min}}{E_{max}-E_{min}} \)
Show Answer & Explanation

Answer: (c) \( m_a=\frac{E_{max}-E_{min}}{E_{max}+E_{min}} \)

Explanation:
1. m = (Emax − Emin)/(Emax + Emin).

Teacher's Note:
1. Recall the basic fact.

Question 11: Which of the following AM-scheme requires the minimum transmitted power and minimum channel bandwidth?
(a) VSB
(b) DSB-SC
(c) AM
(d) SSB
Show Answer & Explanation

Answer: (d) SSB

Explanation:
1. SSB transmits only one sideband with no carrier.

Teacher's Note:
1. Recall the basic fact.

Question 12: Critical frequency that gets reflected back from ionosphere is
(a) same for all layers of the ionosphere
(b) different for different layers of the ionosphere
(c) not dependent on layers of the ionosphere
(d) None of these
Show Answer & Explanation

Answer: (b) different for different layers of the ionosphere

Explanation:
1. The critical frequency depends on the electron density, which differs from layer to layer.

Teacher's Note:
1. Recall the basic fact.

Question 13: Wave obtained on superimposition of audible frequency e.m. wave is known as
(a) carrier wave
(b) high frequency wave
(c) modulating wave
(d) modulated wave
Show Answer & Explanation

Answer: (d) modulated wave

Explanation:
1. Superimposing the message on a carrier gives a modulated wave.

Teacher's Note:
1. Recall the basic fact.

Question 14: For an AM wave, the maximum voltage was found to be 10 V and minimum voltage was 4 V. The modulation index of the wave is
(a) 0.33
(b) 0.43
(c) 0.56
(d) 0.64
Show Answer & Explanation

Answer: (b) 0.43

Explanation:
1. m = (10 − 4)/(10 + 4) = 0.43.

Teacher's Note:
1. Recall the basic fact.

Question 15: Sky wave propagation is not possible for frequencies
(a) equal to 30 MHz
(b) less than 30 MHz
(c) greater than 30 MHz
(d) None of these
Show Answer & Explanation

Answer: (c) greater than 30 MHz

Explanation:
1. Waves above about 30 MHz pass through the ionosphere and are not reflected.

Teacher's Note:
1. Recall the basic fact.

Question 16: In satellite communication, which of the following statement(s) is/are correct? I. The uplink and downlink frequencies are different. II. The orbit of a geostationary satellite lies in the equatorial plane at inclination of 0°.
(a) Both I and II
(b) I only
(c) II only
(d) Neither
Show Answer & Explanation

Answer: (a) Both I and II

Explanation:
1. Uplink and downlink use different frequencies to avoid interference.
2. A geostationary orbit is equatorial and has zero inclination.

Teacher's Note:
1. Recall the basic fact.

Question 17: Global communication is achieved by using
(a) single geostationary satellite
(b) minimum two geostationary satellite 180° apart
(c) minimum three geostationary satellite 120° apart
(d) minimum four geostationary satellite 90° apart
Show Answer & Explanation

Answer: (c) minimum three geostationary satellite 120° apart

Explanation:
1. Three geostationary satellites 120° apart cover the whole globe.

Teacher's Note:
1. Recall the basic fact.

Question 18: In an AM wave, the information is contained within
(a) r.f. carrier wave
(b) only lower and upper side frequencies
(c) both r.f. carrier and side frequencies
(d) None of these
Show Answer & Explanation

Answer: (b) only lower and upper side frequencies

Explanation:
1. The carrier carries no information; the sidebands do.

Teacher's Note:
1. Recall the basic fact.

Question 19: The ratio of Emax − Emin to Emax + Emin is known as
(a) range of modulating signal
(b) amplitude variation of modulating signal
(c) depth of modulation
(d) None of these
Show Answer & Explanation

Answer: (c) depth of modulation

Explanation:
1. This ratio is the depth (index) of modulation.

Teacher's Note:
1. Recall the basic fact.

Question 20: An FM signal has a resting frequency of 105 MHz and highest frequency of 105.03 MHz when modulated by a signal of frequency 5 kHz. The carrier swing is
(a) 25 kHz
(b) 60 kHz
(c) 54 kHz
(d) 75 kHz
Show Answer & Explanation

Answer: (b) 60 kHz

Explanation:
1. Deviation = 105.03 − 105 = 0.03 MHz = 30 kHz.
2. Carrier swing = 2 × 30 = 60 kHz.

Teacher's Note:
1. Recall the basic fact.

Question 21:
Assertion (A): Microwave communication is preferred over optical communication.
Reason (R): Information carrying capacity is directly proportional to bandwidth.
(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.
Show Answer & Explanation

Answer: (d) A is false, but R is true.

Explanation:
1. Optical frequencies have far larger bandwidth, so optical communication carries more information and is preferred; the assertion is false.
2. The reason is true.

Teacher's Note:
1. Compare the two statements.

Question 22: Which mode of communication is most suitable for carrier wave of frequencies around 100 MHz?
(a) Satellite
(b) Ground wave
(c) Line of sight
(d) Ionospheric
Show Answer & Explanation

Answer: (c) Line of sight

Explanation:
1. VHF waves around 100 MHz travel by line of sight (space wave).

Teacher's Note:
1. Recall the basic fact.

Question 23: The function of an amplitude limiter in an FM-receiver is
(a) to reduce the amplitude of the signal to suit IF amplifier
(b) to amplify low frequency signal
(c) to eliminate any change in amplitude of received FM signal
(d) None of these
Show Answer & Explanation

Answer: (c) to eliminate any change in amplitude of received FM signal

Explanation:
1. Since information is in frequency variations, amplitude variations (noise) are clipped.

Teacher's Note:
1. Recall the basic fact.

Question 24: The process of superimposing signal frequency (i.e. audio wave) on the carrier wave is known as
(a) Transmission
(b) Reception
(c) Modulation
(d) Detection
Show Answer & Explanation

Answer: (c) Modulation

Explanation:
1. This process is modulation.

Teacher's Note:
1. Recall the basic fact.

Question 25: Modem is a short form of
(a) modulator-demodulator
(b) multiplexer-demultiplexer
(c) multivibrator-degenerator
(d) None of these
Show Answer & Explanation

Answer: (a) modulator-demodulator

Explanation:
1. MODEM = MOdulator + DEModulator.

Teacher's Note:
1. Recall the basic fact.

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FAQs

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