JEE Questions for Physics Communication System Quiz 4 - MCQExams.com

The energy attenuation in optical fibre is mainly due to
  • Absorption
  • Scattering
  • Both a and b
  • Neither absorption nor scattering
The electromagnetic waves of frequency 2 MHz to 30 MHz are
  • In ground wave propagation
  • In sky wave propagation
  • In micro wave propagation
  • In satellite communication
Coaxial cable offers a band width approximately__________MHz
  • 1
  • 20
  • 250
  • 1000
Modulation is used to…………..
  • Reduce the band width used
  • Seperate the transmission of different areas
  • Ensure that information may be transmitted to long distance
  • Allow the use of practical antennas
An antenna can transmit_____________radiation with more efficiency.
  • Low frequency
  • High frequency
  • Long wave length
  • None of these
For an amplitude modulated wave, the maximum amplitude is found to be 9V while the minimum amplitude is found to be 3V. The modulation index is____________
  • 100%
  • 75%
  • 50%
  • 25%
AM is used for broadcasting because
  • It is more noise innunerable than other modulation system
  • It requires less transmitting power compared with other system
  • It's are avoids receiver complexity....
  • No other modulation system can provide the neccessary band width faithful tranmission
Frequencies in the UHF range normally propagation by means of
  • Ground waves
  • Sky waves
  • Surface waves
  • Space waves
The area to be covered for T.V telecast is doubled. Then the height to transmitting antenna will have to be
  • Doubled
  • Halved
  • Quadrupled
  • Kept unchanged
Which of the following is related to telecommunication
  • X-rays
  • r-rays
  • Sound wave
  • Microwaves
Suppose the amplitude of modulated wave equal to the signal amplitude. Then modulation is
  • 10%
  • 25%
  • 50%
  • 100%
Space waves are generally propagated in
  • UHF
  • VHF
  • HF
  • None of these
If the frequency of 3 KHz has to be transmitted through amplitude modulation. Which of the following frequency should use as a carrier frequency ?
  • 30 Hz
  • 300 Hz
  • 3000 Hz
  • 3 MHz
The range of frequencies allotted for commercial FM radio broadcast is
  • 88 to 108 MHz
  • 88 to 108 KHz
  • 8 to 88 MHz
  • 88 to 108 GHz
The process of superimposing signal frequency on the carrier wave is known as
  • Transmission
  • Reception
  • Modulation
  • Detection

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  • 2)
    Physics-Communication System-64174.png

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In which frequency range, space waves are normally propagated ?
  • HF
  • VHF
  • UHF
  • SHF
If M1 and M2 are the refractive indices of the material of core and cladding of an optical fibre, than the loss of light due to its leakage can be minimised by having

  • Physics-Communication System-64177.png
  • 2)
    Physics-Communication System-64178.png

  • Physics-Communication System-64179.png
  • None of these
Through which mode of propagation, the radio waves can be sent from one place to another ?
  • Ground wave propagation
  • Sky wave propagation
  • Space wave propagation
  • All of them
A radio can tune to any station in the 7.5 MHz to 12 MHz band. What is the corresponding wave length band ?
  • 400m - 250m
  • 40m - 25m
  • 4m - 2.5m
  • None of these
Statement-1 :- sky waves are not used in the transmission of T.V signals
Statement-2 :- T.V signals have a frequency range of 400 to 200 MHz
(a) Statement-1 is true, statement-2 is true.Statement-2 is a correct explanation for statement-1.
(b) Statement-1 is true, statement-2 is true, statement-2 is not a correct explanation for statement-1.
(c) Statement-1 is true, statement-2 is false
(d) Statement-1 is false, statement-2 is true.
  • a
  • b
  • c
  • d
Statement-1 :- Micro waves and not radio waves are used in satellite communication.
Statement-2 :-The wavelength of microwaves is much shorter than that of radio waves. Hence micro wave do not disperse or diffract like radio waves.
(a) Statement-1 is true, statement-2 is true. Statement-2 is a correct explanation for statement-1.
(b) Statement-1 is true, statement-2 is true, statement-2 is not a correct explanation for statement-1.
(c) Statement-1 is true, statement-2 is false
(d) Statement-1 is false, statement-2 is true.
  • a
  • b
  • c
  • d
Statement-1 :- sky wave communication is not suitable for frequencies greater than 30 MHz.
Statement-2 :- High frequency signals die out before reaching the ionosphere.
(a) Statement-1 is true, statement-2 is true. Statement-2 is a correct explanation for statement-1.
(b) Statement-1 is true, statement-2 is true, statement-2 is not a correct explanation for statement-1.
(c) Statement-1 is true, statement-2 is false
(d) Statement-1 is false, statement-2 is true.
  • a
  • b
  • c
  • d
Statement-1 :- Modulated wave is received directly on a head phone
Statement-2 :- High frequency waves are beyond audible range.
(a) Statement-1 is true, statement-2 is true. Statement-2 is a correct explanation for statement-1.
(b) Statement-1 is true, statement-2 is true, statement-2 is not a correct explanation for statement-1.
(c) Statement-1 is true, statement-2 is false
(d) Statement-1 is false, statement-2 is true.
  • a
  • b
  • c
  • d
The refractive inden of the ionosphere
  • Increase as we go from the lower to upper layer of the ionosphere
  • Decrease as we go from the lower to upper layer of the ionosphere
  • Remain the same through out the ionosphere
  • Is equal to unity

Physics-Communication System-64180.png
  • 16 km
  • 32 km
  • 80 km
  • 160 km
A receiving station on the ground is receiving a signal of frequency 10 MHz, then the mode of transmission is
  • Ground wave propagation
  • Sky wave propagation
  • Both ground wave and sky wave propagation
  • Neither ground wave nor sky wave propagation
On a particular day, the maximum frequency reflected from the ionosphere is 8 MHz. On another day it was found to increase to 9 MHz. The ratio of the minimum electron densities of ionosphere on the two days is

  • Physics-Communication System-64181.png
  • 2)
    Physics-Communication System-64182.png

  • Physics-Communication System-64183.png

  • Physics-Communication System-64184.png
Consider an optical communication system operating at λ = 800 nm. Suppose only 1% of the optical source frequency is the available channel bandwidth for optical communication. No. of channels that can be accomodated for transmitting video T.V signals requiring an approximate band width of 4.5 MHz is __________

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  • 2)
    Physics-Communication System-64186.png

  • Physics-Communication System-64187.png

  • Physics-Communication System-64188.png

Physics-Communication System-64189.png
  • 25%
  • 0.25%
  • 400%
  • 40%
0:0:1


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