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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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