Correct4
Incorrect-1
In short wave communication waves of which of the following frequencies will be reflected back by the ionospheric layer, having electron density 10 'per {tex} m {/tex}
{tex} 2 \,M H z {/tex}
10 {tex} M H z {/tex}
{tex} 12 \,{ MHz } {/tex}
{tex} 18 \,{ MHz } {/tex}
Correct4
Incorrect-1
In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be
50 cycles/sec
100 cycles/sec
500 cycles/sec
50,000 cycles/sec
Correct4
Incorrect-1
AM is used for broadcasting because
It is more noise immune than other modulation systems
It requires less transmitting power compared with other systems
Its use avoids receiver complexity
No other modulation system can provide the necessary bandwidth faithful transmission
Correct4
Incorrect-1
Range of frequencies allotted for commercial FM radio broadcast is
{tex} \mathrm {88 \,\,to\,\, 108 }\,\,\ MHz {/tex}
{tex} \mathrm {88 \,\,to\,\, 108 }\,\,\ KHz {/tex}
{tex} \mathrm {8 \,\,to\,\, 88 }\,\,\ MHz {/tex}
{tex} \mathrm {88 \,\,to\,\, 108 }\,\,\ GHz {/tex}
Correct4
Incorrect-1
The velocity factor of a transmission line {tex} x {/tex}. If dielectric constant of the medium is {tex} 2.6 , {/tex} the value of {tex} x {/tex} is
0.26
0.62
2.6
6.2
Correct4
Incorrect-1
The process of superimposing signal frequency (i.e. audio wave) on
the carrier wave is known as
Transmission
Reception
Modulation
Detection
Correct4
Incorrect-1
Long distance short-wave radio broadcasting uses
Ground wave
lonospheric wave
Direct wave
Sky wave
Correct4
Incorrect-1
A step index fibre has a relative refractive index of {tex} 0.88 \% . {/tex} What is the critical angle at the corecladding interface
{tex} 60 ^ { \circ } {/tex}
{tex} 75 ^ { \circ } {/tex}
{tex} 45 ^ { \circ } {/tex}
None of these
Correct4
Incorrect-1
The characteristic impedance of a coaxial cable is of the order of
{tex} {50 \,\Omega} {/tex}
{tex} {200 \,\Omega} {/tex}
{tex} {270\, \Omega} {/tex}
None of these
Correct4
Incorrect-1
In which frequency range, space waves are normally propagated
{tex} \mathrm { HF } {/tex}
{tex} \mathrm { VHF } {/tex}
{tex} \mathrm {UHF} {/tex}
{tex} \mathrm { SHF } {/tex}
Correct4
Incorrect-1
If {tex} \mu {/tex} and {tex} \mu_{1}{/tex} 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
{tex} \mu > \mu_{1} {/tex}
{tex} \mu < \mu_{1} {/tex}
{tex} \mu = \mu_{1} {/tex}
None of these
Correct4
Incorrect-1
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
Correct4
Incorrect-1
A laser beam of pulse power 10 watt is focussed on an object are 10 cm. The energy flux in wattl {tex} c m {/tex} at the point of focus is
10{tex}^{20}{/tex}
10{tex}^{16}{/tex}
10{tex}^{8}{/tex}
10{tex}^{4}{/tex}
Correct4
Incorrect-1
The carrier frequency generated by a tank circuit containing 1 {tex} n F {/tex} capacitor and {tex} 10 \mu H {/tex} inductor is
{tex} 1592 \mathrm{ Hz } {/tex}
{tex} 1592 \mathrm { MHz } {/tex}
{tex} 1592 \mathrm { kHz } {/tex}
{tex} 159.2 \mathrm { Hz } {/tex}
Correct4
Incorrect-1
Broadcasting antennas are generally
Omnidirectional type
Vertical type
Horizontal type
None of these
Correct4
Incorrect-1
For television broadcasting, the frequency employed is normally
{tex} 30 - 300\, M H z {/tex}
{tex} 30 - 300\, G H z {/tex}
{tex} 30 - 300 \,K H z {/tex}
{tex} 30 - 300 \,H z {/tex}
Correct4
Incorrect-1
The radio waves of frequency {tex} 300 \mathrm{ MHz } {/tex} to {tex} 3000 \mathrm{ MHz } {/tex} belong to
High frequency band
Very high frequency band
Ultra high frequency band
Super high frequency band
Correct4
Incorrect-1
An antenna behaves as resonant circuit only when its length is
{tex} \frac { \lambda } { 2 } {/tex}
{tex} \frac { \lambda } { 4 } {/tex}
{tex} \lambda {/tex}
{tex} \frac { \lambda } { 2 } {/tex} or integral multiple of {tex} \frac { \lambda } { 2 } {/tex}
Correct4
Incorrect-1
Maximum useable frequency (MUF) in F region layer is {tex} x , {/tex} when the critical frequency is {tex} 60 \mathrm { MHz } {/tex} and the angle of incidence is {tex} 70 ^ { \circ } . {/tex} Then {tex} x {/tex} is
{tex} 150 \mathrm { MHz } {/tex}
{tex} 170 \mathrm{ MHz} {/tex}
{tex} 175 \mathrm { MHz } {/tex}
{tex} 190\mathrm { MHz } {/tex}
Correct4
Incorrect-1
The electromagnetic waves of frequency {tex} 2 \mathrm{ MHz } {/tex} to {tex} 30 \mathrm { MHz } {/tex} are
In ground wave propagation
In sky wave propagation
In microwave propagation
In Satellite communication
Correct4
Incorrect-1
A laser is a coherent source because it contains
Many wavelengths
Uncoordinated wave of a particular wavelength
Coordinated wave of many wavelengths
Coordinated waves of a particular wavelength
Correct4
Incorrect-1
The attenuation in optical fibre is mainly due to
Absorption
Scattering
Neither absorption nor scattering
Both (a) and (b)
Correct4
Incorrect-1
The maximum distance upto which TV transmission from a TV tower of height {tex} h {/tex} can be received is proportional to
h{tex}^{1/2}{/tex}
h{tex}^{2}{/tex}
h{tex}^{6}{/tex}
h{tex} {/tex}
Correct4
Incorrect-1
A laser beam is used for carrying out surgery because it
Is highly monochromatic
Is highly coherent
Is highly directional
Can be sharply focussed
Correct4
Incorrect-1
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
