JEE Main & Advanced Physics Communication System / संचार तंत्र Question Bank

done Communication Total Questions - 52

• question_answer1)
  In short wave communication waves of which of the following frequencies will be reflected back by the ionospheric layer, having electron density 1011 per m3  [AIIMS 2003]
  A)
             2 MHz done clear
  B)
             10 MHz done clear
  C)
             12 MHz                                    done clear
  D)
             18 MHz done clear
  View Solution play_arrow

• question_answer2)
  In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be  [AMU 1996]
  A)
             50 cycles/sec                         done clear
  B)
             100 cycles/sec done clear
  C)
             500 cycles/sec                       done clear
  D)
             50,000 cycles/sec done clear
  View Solution play_arrow

• question_answer3)
  AM is used for broadcasting because 
  A)
             It is more noise immune than other modulation systems done clear
  B)
             It requires less transmitting power compared with other systems done clear
  C)
             Its use avoids receiver complexity done clear
  D)
             No other modulation system can provide the necessary bandwidth faithful transmission done clear
  View Solution play_arrow

• question_answer4)
  Range of frequencies allotted for commercial FM radio broadcast is                                         [MNR 1997]
  A)
             88 to 108 MHz                       done clear
  B)
             88 to 108 kHz done clear
  C)
             8 to 88 MHz                           done clear
  D)
             88 to 108 GHz done clear
  View Solution play_arrow

• question_answer5)
  The velocity factor of a transmission line x. If dielectric constant of the medium is 2.6, the value of x is [AFMC 1995]
  A)
             0.26                                           done clear
  B)
             0.62 done clear
  C)
             2.6  done clear
  D)
             6.2 done clear
  View Solution play_arrow

• question_answer6)
  The process of superimposing signal frequency (i.e. audio wave) on the carrier wave is known as              [AIIMS 1987]
  A)
             Transmission                         done clear
  B)
             Reception done clear
  C)
             Modulation                           done clear
  D)
             Detection done clear
  View Solution play_arrow

• question_answer7)
  Long distance short-wave radio broadcasting uses  [AFMC 1996]
  A)
             Ground wave                       done clear
  B)
             Ionospheric wave done clear
  C)
             Direct wave                           done clear
  D)
             Sky wave done clear
  View Solution play_arrow

• question_answer8)
  A step index fibre has a relative refractive index of 0.88%. What is the critical angle at the corecladding interface [Manipal 2003]
  A)
             60° done clear
  B)
             75° done clear
  C)
             45° done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer9)
  The characteristic impedance of a coaxial cable is of the order of                                               [CPMT 2003]
  A)
             50 W                                         done clear
  B)
             200 W done clear
  C)
             270 W                                       done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer10)
  In which frequency range, space waves are normally propagated                                             [EAMCET 2002]
  A)
             HF  done clear
  B)
             VHF done clear
  C)
             UHF                                          done clear
  D)
             SHF done clear
  View Solution play_arrow

• question_answer11)
  If m1 and m2 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                        [BVP 2003]
  A)
             m1 > m2                                     done clear
  B)
             m1 < m2 done clear
  C)
             m1 = m2                                     done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer12)
  Through which mode of propagation, the radio waves can be sent from one place to another     [JIPMER 2003]
  A)
             Ground wave propagation  done clear
  B)
             Sky wave propagation done clear
  C)
             Space wave propagation done clear
  D)
             All of them done clear
  View Solution play_arrow

• question_answer13)
  A laser beam of pulse power 1012 watt is focussed on an object are 10?4 cm2. The energy flux in watt/ cm2 at the point of focus is                                                       [AFMC 2003]
  A)
             1020                                           done clear
  B)
             1016 done clear
  C)
             108 done clear
  D)
             104 done clear
  View Solution play_arrow

• question_answer14)
  The carrier frequency generated by a tank circuit containing 1 nF capacitor and 10 mH inductor is                [AFMC 2003]
  A)
             1592 Hz                                    done clear
  B)
             1592 MHz done clear
  C)
             1592 kHz                                 done clear
  D)
             159.2 Hz done clear
  View Solution play_arrow

• question_answer15)
  Broadcasting antennas are generally                    [AFMC 2003]
  A)
             Omnidirectional type        done clear
  B)
             Vertical type done clear
  C)
             Horizontal type                    done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer16)
  For television broadcasting, the frequency employed is normally                                              [AMU 2002]
  A)
             30-300 MHz                           done clear
  B)
             30-300 GHz done clear
  C)
             30-300 KHz                             done clear
  D)
             30-300 Hz done clear
  View Solution play_arrow

• question_answer17)
  The radio waves of frequency 300 MHz to 3000 MHz belong to                                   [AMU 2002]
  A)
             High frequency band done clear
  B)
             Very high frequency band done clear
  C)
             Ultra high frequency band done clear
  D)
             Super high frequency band done clear
  View Solution play_arrow

• question_answer18)
  An antenna behaves as resonant circuit only when its length is                                                  [MNR 2002]
  A)
             \[\frac{\lambda }{2}\] done clear
  B)
             \[\frac{\lambda }{4}\] done clear
  C)
             l done clear
  D)
             \[\frac{\lambda }{2}\] or integral multiple of \[\frac{\lambda }{2}\] done clear
  View Solution play_arrow

• question_answer19)
  Maximum useable frequency (MUF) in F-region layer is x, when the critical frequency is 60 MHz and the angle of incidence is 70°. Then x is                                                  [Himachal PMT 2003]
  A)
             150 MHz                                  done clear
  B)
             170 MHz done clear
  C)
             175 MHz                                  done clear
  D)
             190 MHz done clear
  View Solution play_arrow

• question_answer20)
  The electromagnetic waves of frequency 2 MHz to 30 MHz are                                                  [Haryana PMT 2003]
  A)
             In ground wave propagation done clear
  B)
             In sky wave propagation done clear
  C)
             In microwave propagation done clear
  D)
             In satellite communication done clear
  View Solution play_arrow

• question_answer21)
  A laser is a coherent source because it contains  [JIPMER 2003]
  A)
             Many wavelengths done clear
  B)
             Uncoordinated wave of a particular wavelength done clear
  C)
             Coordinated wave of many wavelengths done clear
  D)
             Coordinated waves of a particular wavelength done clear
  View Solution play_arrow

• question_answer22)
  The attenuation in optical fibre is mainly due to [AFMC 2003]
  A)
             Absorption done clear
  B)
             Scattering done clear
  C)
             Neither absorption nor scattering done clear
  D)
             Both (a) and (b) done clear
  View Solution play_arrow

• question_answer23)
  The maximum distance upto which TV transmission from a TV tower of height h can be received is proportional to  [AIIMS 2003]
  A)
             h1/2                                            done clear
  B)
             h done clear
  C)
             h3/2                                            done clear
  D)
             h2 done clear
  View Solution play_arrow

• question_answer24)
  A laser beam is used for carrying out surgery because it  [AIIMS 2003]
  A)
             Is highly monochromatic done clear
  B)
             Is highly coherent done clear
  C)
             Is highly directional            done clear
  D)
             Can be sharply focussed done clear
  View Solution play_arrow

• question_answer25)
  Laser beams are used to measure long distances because  [DCE 2002, 03]
  A)
             They are monochromatic done clear
  B)
             They are highly polarised done clear
  C)
             They are coherent done clear
  D)
             They have high degree of parallelism done clear
  View Solution play_arrow

• question_answer26)
  An oscillator is producing FM waves of frequency 2 kHz with a variation of 10 kHz. What is the modulating index [DCE 2004]
  A)
             0.20                                           done clear
  B)
             5.0 done clear
  C)
             0.67                                           done clear
  D)
             1.5 done clear
  View Solution play_arrow

• question_answer27)
  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
  A)
             10%                                           done clear
  B)
             20% done clear
  C)
             25%                                           done clear
  D)
             50% done clear
  View Solution play_arrow

• question_answer28)
  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
  A)
             1490, 1510                              done clear
  B)
             1510, 1490 done clear
  C)
             \[\frac{1}{1490},\frac{1}{1510}\]                                      done clear
  D)
             \[\frac{1}{1510},\frac{1}{1490}\] done clear
  View Solution play_arrow

• question_answer29)
  What is the modulation index of an over modulated wave
  A)
             1     done clear
  B)
             Zero done clear
  C)
             < 1  done clear
  D)
             > 1 done clear
  View Solution play_arrow

• question_answer30)
  Basically, the product modulator is
  A)
             An amplifier                          done clear
  B)
             A mixer done clear
  C)
             A frequency separator     done clear
  D)
             A phase separator done clear
  View Solution play_arrow

• question_answer31)
  If fa and ff represent the carrier wave frequencies for amplitude and frequency modulations respectively, then
  A)
             \[{{f}_{a}}>{{f}_{f}}\]        done clear
  B)
             \[{{f}_{a}}<{{f}_{f}}\] done clear
  C)
             \[{{f}_{a}}\approx {{f}_{f}}\] done clear
  D)
             \[{{f}_{a}}\ge {{f}_{f}}\] done clear
  View Solution play_arrow

• question_answer32)
  Which of the following is the disadvantage of FM over AM
  A)
             Larger band width requirement done clear
  B)
             Larger noise done clear
  C)
             Higher modulation power done clear
  D)
             Low efficiency done clear
  View Solution play_arrow

• question_answer33)
  If a number of sine waves with modulation indices n1, n2, n3 ........ modulate a carrier wave, then total modulation index (n) of the wave is
  A)
             n1 + n2 .... + 2(n1 + n2.....) done clear
  B)
             \[\sqrt{{{n}_{1}}-{{n}_{2}}+{{n}_{3}}..........}\] done clear
  C)
             \[\sqrt{n_{1}^{2}+n_{2}^{2}+n_{3}^{2}.........}\] done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer34)
  An AM wave has 1800 watt of total power content, For 100% modulation the carrier should have power content equal to
  A)
             1000 watt                               done clear
  B)
             1200 watt done clear
  C)
             1500 watt                               done clear
  D)
             1600 watt done clear
  View Solution play_arrow

• question_answer35)
  The frequency of a FM transmitter without signal input is called
  A)
             Lower side band frequency done clear
  B)
             Upper side band frequency done clear
  C)
             Resting frequency done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer36)
  What type of modulation is employed in India for radio transmission
  A)
             Amplitude modulation     done clear
  B)
             Frequency modulation done clear
  C)
             Pulse modulation                done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer37)
  When the modulating frequency is doubled, the modulation index is halved and the modulating voltage remains constant, the modulation system is
  A)
             Amplitude modulation     done clear
  B)
             Phase modulation done clear
  C)
             Frequency modulation     done clear
  D)
             All of the above done clear
  View Solution play_arrow

• question_answer38)
  An antenna is a device
  A)
             That converts electromagnetic energy into radio frequency signal done clear
  B)
             That converts radio frequency signal into electromagnetic energy done clear
  C)
             That converts guided electromagnetic waves into free space electromagnetic waves and vice-versa done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer39)
  While tuning in a certain broadcast station with a receiver, we are actually
  A)
             Varying the local oscillator frequency done clear
  B)
             Varying the frequency of the radio signal to be picked up done clear
  C)
             Tuning the antenna done clear
  D)
             None of these done clear
  View Solution play_arrow

• question_answer40)
  Indicate which one of the following system is digital
  A)
             Pulse position modulation done clear
  B)
             Pulse code modulation done clear
  C)
             Pulse width modulation done clear
  D)
             Pulse amplitude modulation done clear
  View Solution play_arrow

• question_answer41)
  In a communication system, noise is most likely to affect the signal
  A)
             At the transmitter done clear
  B)
             In the channel or in the transmission line done clear
  C)
             In the information source done clear
  D)
             At the receiver done clear
  View Solution play_arrow

• question_answer42)
  The waves used in telecommunication are
  A)
             IR    done clear
  B)
             UV done clear
  C)
             Microwave                            done clear
  D)
             Cosmic rays done clear
  View Solution play_arrow

• question_answer43)
  In an FM system a 7 kHz signal modulates 108 MHz carrier so that frequency deviation is 50 kHz. The carrier swing is
  A)
             7.143                                        done clear
  B)
             8 done clear
  C)
             0.71                                           done clear
  D)
             350 done clear
  View Solution play_arrow

• question_answer44)
  Consider telecommunication through optical fibres. Which of the following statements is not true           [AIEEE 2003]
  A)
             Optical fibres may have homogeneous core with a suitable cladding done clear
  B)
             Optical fibres can be of graded refractive index done clear
  C)
             Optical fibres are subject to electromagnetic interference from outside done clear
  D)
             Optical fibres have extremely low transmission loss done clear
  View Solution play_arrow

• question_answer45)
  The phenomenon by which light travels in an optical fibres is                                                      [DCE 2001]
  A)
             Reflection                              done clear
  B)
             Refraction done clear
  C)
             Total internal reflection    done clear
  D)
             Transmission done clear
  View Solution play_arrow

• question_answer46)
  Television signals on earth cannot be received at distances greater than 100 km from the transmission station. The reason behind this is that                                                            [DCE 1995]
  A)
             The receiver antenna is unable to detect the signal at a distance greater than 100 km done clear
  B)
             The TV programme consists of both audio and video signals done clear
  C)
             The TV signals are less powerful than radio signals done clear
  D)
             The surface of earth is curved like a sphere done clear
  View Solution play_arrow

• question_answer47)
  Advantage of optical fibre                                            [DCE 2005]
  A)
             High bandwidth and EM interference done clear
  B)
             Low bandwidth and EM interference done clear
  C)
             High band width, low transmission capacity and no EM interference done clear
  D)
             High bandwidth, high data transmission capacity and no EM interference done clear
  View Solution play_arrow

• question_answer48)
  In frequency modulation                                  [Kerala PMT 2005]
  A)
             The amplitude of modulated wave varies as frequency of carrier wave done clear
  B)
             The frequency of modulated wave varies as amplitude of modulating wave done clear
  C)
             The amplitude of modulated wave varies as amplitude of carrier wave done clear
  D)
             The frequency of modulated wave varies as frequency of modulating wave done clear
  E)
  (e)     The frequency of modulated wave varies as frequency of carrier wave done clear
  View Solution play_arrow

• question_answer49)
  Audio signal cannot be transmitted because  [Kerala PMT 2005]
  A)
             The signal has more noise done clear
  B)
             The signal cannot be amplified for distance communication done clear
  C)
             The transmitting antenna length is very small to design done clear
  D)
             The transmitting antenna length is very large and impracticable done clear
  E)
  (e)     The signal is not a radio signal done clear
  View Solution play_arrow

• question_answer50)
  In which of the following remote sensing technique is not used                                                 [Kerala PMT 2005]
  A)
             Forest density                      done clear
  B)
             Pollution done clear
  C)
             Wetland mapping               done clear
  D)
             Medical treatment done clear
  View Solution play_arrow

• question_answer51)
  For sky wave propagation of a 10 MHz signal, what should be the minimum electron density in ionosphere [AIIMS 2005]
  A)
             ~ 1.2 ´ 1012 m?3                    done clear
  B)
             ~ 106 m?3  done clear
  C)
             ~ 1014 m?3                               done clear
  D)
             ~ 1022 m?3 done clear
  View Solution play_arrow

• question_answer52)
  What should be the maximum acceptance angle at the aircore interface of an optical fibre if n1 and n2 are the refractive indices of the core and the cladding, respectively  [AIIMS 2005]
  A)
             \[{{\sin }^{-1}}({{n}_{2}}/{{n}_{1}})\]                             done clear
  B)
             \[{{\sin }^{-1}}\sqrt{n_{1}^{2}-n_{2}^{2}}\] done clear
  C)
             \[\left[ {{\tan }^{-1}}\frac{{{n}_{2}}}{{{n}_{1}}} \right]\]      done clear
  D)
             \[\left[ {{\tan }^{-1}}\frac{{{n}_{1}}}{{{n}_{2}}} \right]\] done clear
  View Solution play_arrow