Physics Objective Questions and Answers: Communication System
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Multiple Choice Questions
Assertion (A): Amplification is necessary to compensate for the attenuation of the signal in communication system.
Reason (R): Amplification is the process of increasing the amplitude and consequently the strength of signal using an electronic circuit.
(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: (a) Both A and R are true, and R is the correct explanation of A.
Explanation:
1. Amplification restores the strength lost by attenuation, as the reason explains.
Teacher's Note:
1. Compare the two statements.
(a) transmitter
(b) transducer
(c) processor
(d) repeater
Show Answer & Explanation
Answer: (d) repeater
Explanation:
1. A repeater picks up and retransmits the signal over a longer range.
Teacher's Note:
1. Recall the basic fact.
(a) amplitude modulated
(b) frequency modulated
(c) phase modulated
(d) pulse modulated
Show Answer & Explanation
Answer: (b) frequency modulated
Explanation:
1. The TV sound signal is frequency modulated.
Teacher's Note:
1. Recall the basic fact.
(a) \( E_c \)
(b) \( mE_c \)
(c) \( \frac{mE_c}{2} \)
(d) \( 2mE \)
Show Answer & Explanation
Answer: (c) \( \frac{mE_c}{2} \)
Explanation:
1. Each side band has amplitude mE_c/2.
Teacher's Note:
1. Recall the basic fact.
(a) 1.32 kW
(b) 1.56 kW
(c) 1.84 kW
(d) 1.96 kW
Show Answer & Explanation
Answer: (a) 1.32 kW
Explanation:
1. P_t = P_c(1 + m²/2) = 1 × (1 + 0.32) = 1.32 kW.
Teacher's Note:
1. Recall the basic fact.
(a) increases
(b) decreases
(c) remains the same
(d) both (a) and (b)
Show Answer & Explanation
Answer: (a) increases
Explanation:
1. Orbital speed v = √(GM/r) increases as the radius decreases.
Teacher's Note:
1. Recall the basic fact.
(a) modulation is halved
(b) carrier swing is halved
(c) modulation is doubled
(d) modulation index is decreased
Show Answer & Explanation
Answer: (c) modulation is doubled
Explanation:
1. Modulation index (and percent modulation) is proportional to frequency deviation.
Teacher's Note:
1. Recall the basic fact.
(a) to amplify signal
(b) to reduce its frequency level
(c) to modulate signal
(d) to demodulate signal
Show Answer & Explanation
Answer: (d) to demodulate signal
Explanation:
1. A detector recovers the message signal from the modulated wave.
Teacher's Note:
1. Recall the basic fact.
(a) less than R.I of cladding
(b) more than R.I of cladding
(c) equal to R.I of cladding
(d) halved to R.I of cladding
Show Answer & Explanation
Answer: (b) more than R.I of cladding
Explanation:
1. Total internal reflection needs the core to have the higher refractive index.
Teacher's Note:
1. Recall the basic fact.
(a) stratosphere
(b) mesosphere
(c) troposphere
(d) ionosphere
Show Answer & Explanation
Answer: (c) troposphere
Explanation:
1. Weather and water vapour are in the troposphere.
Teacher's Note:
1. Recall the basic fact.
Assertion (A): The loss of strength of a signal while propagating through a medium is known as attenuation.
Reason (R): Transmitter helps to avoid attenuation.
(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: (c) A is true, but R is false.
Explanation:
1. The assertion is the definition of attenuation.
2. A transmitter does not avoid attenuation (repeaters and amplifiers compensate it), so the reason is incorrect.
Teacher's Note:
1. Compare the two statements.
(a) 1010 kHz or 990 kHz
(b) 1010 MHz or 1010 MHz
(c) 110 kHz or 990 kHz
(d) 110 MHz or 990 MHz
Show Answer & Explanation
Answer: (a) 1010 kHz or 990 kHz
Explanation:
1. SSB keeps one sideband: 1000 ± 10 kHz, that is 1010 kHz or 990 kHz.
Teacher's Note:
1. Recall the basic fact.
(a) Radio telegraph-VSB
(b) Television-SSB
(c) Radio broadcast-AM
(d) Radar-AM
Show Answer & Explanation
Answer: (c) Radio broadcast-AM
Explanation:
1. Radio broadcasting uses AM; TV picture uses VSB.
Teacher's Note:
1. Recall the basic fact.
| Column I | Column II |
|---|---|
| (A) Attenuation | (1) The process of increasing the amplitude |
| (B) Amplification | (2) The loss of strength of a signal |
| (C) Bandwidth | (3) The process of retrieval of information from the carrier wave |
| (D) Demodulation | (4) The frequency range over which an equipment operates |
(a) A-2, B-4, C-1, D-3
(b) A-1, B-2, C-4, D-3
(c) A-3, B-1, C-4, D-2
(d) A-2, B-1, C-4, D-3
Show Answer & Explanation
Answer: (d) A-2, B-1, C-4, D-3
Explanation:
1. Attenuation is the loss of strength.
2. Amplification increases amplitude.
3. Bandwidth is the frequency range.
4. Demodulation recovers information.
Teacher's Note:
1. Recall each definition.
(a) low efficiency
(b) noise reception
(c) operating range is small
(d) all of the above
Show Answer & Explanation
Answer: (d) all of the above
Explanation:
1. AM is inefficient, noisy and has a small operating range.
Teacher's Note:
1. Recall the basic fact.
(a) radio broadcast transmitter
(b) radio telegraph transmitter
(c) navigation transmitter
(d) None of these
Show Answer & Explanation
Answer: (a) radio broadcast transmitter
Explanation:
1. Such broadcasting is done by radio broadcast transmitters.
Teacher's Note:
1. Recall the basic fact.
(a) IR
(b) UV
(c) Microwave
(d) Cosmic rays
Show Answer & Explanation
Answer: (c) Microwave
Explanation:
1. Microwaves are used in satellite and mobile communication.
Teacher's Note:
1. Recall the basic fact.
(a) I and II
(b) I, II and III
(c) II and III
(d) I and III
Show Answer & Explanation
Answer: (b) I, II and III
Explanation:
1. All three statements are correct.
Teacher's Note:
1. Recall the basic fact.
(a) longer antenna for the AM channel and shorter for the FM
(b) shorter antenna for the AM channel and longer for FM
(c) same length antenna will work for both
(d) information given is not enough to say which one to use for which
Show Answer & Explanation
Answer: (a) longer antenna for the AM channel and shorter for the FM
Explanation:
1. Antenna length is proportional to the wavelength.
2. AM (1020 kHz) has the longer wavelength, so it needs the longer antenna.
Teacher's Note:
1. Recall the basic fact.
(a) 1
(b) Zero
(c) < 1
(d) > 1
Show Answer & Explanation
Answer: (d) > 1
Explanation:
1. Over modulation means m > 1.
Teacher's Note:
1. Recall the basic fact.
(a) actual frequency deviation > maximum allowed frequency deviation
(b) actual frequency deviation = maximum allowed frequency deviation
(c) actual frequency deviation ≥ maximum allowed frequency deviation
(d) actual frequency deviation < maximum allowed frequency deviation
Show Answer & Explanation
Answer: (b) actual frequency deviation = maximum allowed frequency deviation
Explanation:
1. 100% modulation means the deviation equals the maximum allowed deviation.
Teacher's Note:
1. Recall the basic fact.
(a) pulse spacing is reduced
(b) pulse amplitude is increased
(c) pulse width is increased
(d) repeater stations are used
Show Answer & Explanation
Answer: (d) repeater stations are used
Explanation:
1. Regenerative repeaters restore the pulses along a long path.
Teacher's Note:
1. Recall the basic fact.
(a) 25%
(b) 41.6%
(c) 50%
(d) 75%
Show Answer & Explanation
Answer: (b) 41.6%
Explanation:
1. m = Am/Ac = 25/60 = 0.416 = 41.6%.
Teacher's Note:
1. Recall the basic fact.
(a) Mobile phone
(b) Walky-talky
(c) Loud speaker
(d) Radio
Show Answer & Explanation
Answer: (a) Mobile phone
Explanation:
1. A mobile phone transmits and receives simultaneously.
Teacher's Note:
1. Recall the basic fact.
(a) omnidirectional type
(b) vertical type
(c) horizontal type
(d) None of these
Show Answer & Explanation
Answer: (a) omnidirectional type
Explanation:
1. Broadcast antennas radiate equally in all horizontal directions.
Teacher's Note:
1. Recall the basic fact.
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FAQs
You can get most exhaustive JEE Physics Communication System MCQs Set 11 for free on StudiesToday.com. These MCQs for JEE Physics are updated for the 2026-27 academic session as per JEE examination standards.
Yes, our JEE Physics Communication System MCQs Set 11 include the latest type of questions, such as Assertion-Reasoning and Case-based MCQs. 50% of the JEE paper is now competency-based.
By solving our JEE Physics Communication System MCQs Set 11, JEE students can improve their accuracy and speed which is important as objective questions provide a chance to secure 100% marks in the Physics.
Yes, Physics MCQs for JEE have answer key and brief explanations to help students understand logic behind the correct option as its important for 2026 competency-focused JEE exams.
Yes, you can also access online interactive tests for JEE Physics Communication System MCQs Set 11 on StudiesToday.com as they provide instant answers and score to help you track your progress in Physics.