JEE Questions for Physics Communication System Quiz 6 - MCQExams.com

The effective power radiated by an antenna varies
  • Inversely as the lenght of antenna
  • Inversely as the square of the length of the antenna
  • Directly as the lenght of antenna
  • Directly as the square of the lenght of the antenna
A 1000 KHz carrier is modulated with 800 KHz audio signals What are the frequencies of first pair side branch ?

  • Physics-Communication System-64223.png
  • 2)
    Physics-Communication System-64224.png

  • Physics-Communication System-64225.png

  • Physics-Communication System-64226.png
The critical frequency of player is 50 MHz when angle of incidence is 74o What is the maximum unable frequency ?

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  • 2)
    Physics-Communication System-64228.png

  • Physics-Communication System-64229.png

  • Physics-Communication System-64230.png

Physics-Communication System-64231.png
  • 1.2
  • 1.44
  • 0.69
  • 1.6
How long will it take to transmit the information 30km away in space ?
  • 0.1 m s
  • 0.1 µ s
  • 0.1 n s
  • 0.1 p s
What is the velocity of electromagnetic wave in a good conductor ?

  • Physics-Communication System-64232.png
  • 2)
    Physics-Communication System-64233.png
  • High
  • Very low
If 'fm' is the modulation frequency in Fm the modulation index is proportional to
  • fm
  • 2)
    Physics-Communication System-64234.png

  • Physics-Communication System-64235.png

  • Physics-Communication System-64236.png
For 100% modulation, What is the value of minimum amplitude ( Emin ) of the modulated wave ?
  • Zero
  • 1
  • 2
  • 3
When electromagnetic waves enter the ionised layer of ionosphere, the relative permitting of the ionised layer
  • Remain constant
  • Appears to decrease
  • Appears to increase
  • Changer randomly
In which of the following media the wave propagation occurs with out attenuation ?
  • Conductor
  • Perfect dielectric medium
  • Semi conductor
  • None of the above
The step index fibre has a relative refractive index difference of 0.86% what is the critical angle at the core cladding interface ?
  • 28.4o
  • 82.4o
  • 24.8o
  • 75.6o
A silicon optical fibre has a core refractive index of 1.50 and a cladding refractive index 1.47 what is the numerical aperture of the fibre ?
  • 0.90
  • 0.60
  • 0.45
  • 0.30
Which of the following alternative is not nature Noise ?
  • Thunder of light
  • Radiation coming from sun
  • Radiation coming from stars
  • Radiation produced by flickering of tube light
In optical fibre communication, the APD semi conductor device is used
  • to convert radio single into optical single
  • to obtain intanxty modulated signal
  • to convert optical signal into electrical signal
  • to convert optical signal into electrical signal
Phase difference between space current and capacitive current is

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  • 2)
    Physics-Communication System-64238.png

  • Physics-Communication System-64239.png

  • Physics-Communication System-64240.png
Refractive index of ionosphere is
  • One
  • More than one
  • less than one
  • Zero
In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be
  • 50 cycles/s
  • 100 cycles/s
  • 500 cycles/s
  • 50,000 cycles/s
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 velocity factor of a transmission line is x. If dielectric constant of the medium is 2.6, value of x is
  • 0.26
  • 0.62
  • 2.6
  • 6.2
The process of superimposing signal frequency (i. e., audio wave) on the carrier wave is known as
  • Transmission
  • Reception
  • Modulation
  • Detection
Long distance short-wave radio broadcasting uses
  • Ground wave
  • Ionospheric wave
  • Direct wave
  • Sky wave
A step index fibre has a relative refractive index of 0.88%. What is the critical angle at the corecladding interface?
  • 60°
  • 75°
  • 45°
  • None of these
If µ1 and µ2 are the refractive indices of the materials of core and cladding of an optical fibre, then the loss of light due to its leakage can be minimised by having
  • µ1 > µ2
  • µ1 < µ2
  • µ1 = µ2
  • None of these
For television broadcasting, the frequency employed is normally
  • 30-300 MHz
  • 30-300 GHz
  • 30-300 kHz
  • 30-300 Hz
The radio waves of frequency 300 MHz to 3000 MHz belong to
  • High Frequency band
  • Very high frequency band
  • Ultra high frequency band
  • Super high frequency band
An antenna behaves as resonant circuit only when its length is

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  • 2)
    Physics-Communication System-64244.png

  • Physics-Communication System-64245.png

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Laser beams are used to measure long distances because
  • They are monochromatic
  • They are highly polarised
  • They are coherent
  • They have high degree of parallelism
An oscillator is producing FM waves of frequency 2 KHz with a variation of 10 KHz. What is the modulating index ?
  • 0.20
  • 5.0
  • 0.67
  • 1.5
The maximum peak to peak voltage of an AM wire is 24 mV and the minimum peak to peak voltage is 8 mV. The modulation factor is
  • 10%
  • 20%
  • 25%
  • 50%
Sinusoidal carrier voltage of frequency 1.5 MHz and amplitude 50 V is amplitude modulated by sinusoidal voltage of frequency 10 kHz producing 50% modulation. The lower and upper side-band frequencies in kHz are
  • 1490, 1510
  • 1510, 1490

  • Physics-Communication System-64249.png

  • Physics-Communication System-64250.png
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