Q.1
Frequencies in the UHF range normally propagation by means of
  • a) ground waves
  • b) sky waves
  • c) surface waves
  • d) space waves
Q.2
The area to be covered for T.V telecast is doubled. Then the height to transmittingantenna will have to be
  • a)doubled
  • b) halved
  • c)quadrupled
  • d)kept unchanged
Q.3
Suppose the amplitude of modulated wave equal to the signal amplitude. Then modulation is
  • a)10%
  • b)25%
  • c)50%
  • d)100%
Q.4
Space waves are generally propagated in
  • a)UHF
  • b) VHF
  • c)HF
  • d)None of there
Q.5
If the frequency of 3 KHz has to be transmitted through amplitude modulation. Whichof the following frequency should use as a carrier frequency ?
  • a) 30 Hz
  • b) 300 Hz
  • c) 3000 Hz
  • d) 3 MHz
Q.6
The range of frequencies allotted for commercial FM radio broadcast is
  • a)88 to 108 MHz
  • b)88 to 108 KHz
  • c)8 to 88 MHz
  • d)88 to 108 GHz
Q.7
The process of super imposing signal frequency on the carrier wave is known as
  • a) transmission
  • b) reception
  • c)modulation
  • d)detection
Q.8
A T.V tower has a height 150m. What is the population density around the T.V towerif the total population covered is 50 lakh ? (Radius of earth=6.4× 106 m)
  • a) 82.6/km²
  • b) 800.6/km²
  • c)828.6/km²
  • d)876.6/km²
Q.9
If M1 and M2 are the refractive indices of the material of core and cladding of an opticalfibre, than the loss of light due to its leakage can be minimized by having
  • a) M1 > M2
  • b) M1 < M2
  • d) None of these
  • c) M₁=M₂
Q.10
Through which mode of propagation, the radio waves can be sent from one place toanother ?
  • a)ground wave propagation
  • b) sky wave propagation
  • c)space wave propagation
  • d)all of them
Q.11
A radio can tune to any station in the 7.5 MHz to 12 MHz band. What is thecorresponding wave length band ?
  • a)400m - 250m
  • b)40m - 25m
  • c)4m - 2.5m
  • d)None of these
Q.12
Consider an optical communication system operating at λ=800 nm . Suppose only 1% ofthe optical source frequency is the available channel bandwidth for opticalcommunication. No. of channels that can be accommodated for transmitting video T.Vsignals requiring an approximate band width of 4.5 MHz is .
  • a)3.8×1014
  • b) 3.8×1012
  • c)8.4×105
  • d)1.71×107
Q.13
A signal em=20sin 2000 πt amplitude modulates a carries wave ec=80 sin 2000 00 πt .The percentage of modulation is
  • a) 25%
  • b) 0.25%
  • c) 400%
  • d) 40%
Q.14
A transmitting antenna at the top of a tower has a height of 50m and the height of thereceiving antenna is 32m. The maximum distance between them for satisfactorycommunication in line of right mode is . Given radius of earth R=6400 km
  • a)25.29×103km
  • b)20.23×103km
  • c)45.5km
  • d)None of these.
Q.15
The characteristic impendence of a co-axial cable is between .
  • a)10Ωto 20Ω
  • b)20Ω to 30Ω
  • c)30Ω to 60Ω
  • d)50Ωto 70Ω
Q.16
In order to cover a circular region of radios 128 km, by a TV transmitter, What must bethe height of the transmitting antenna ?
  • a)79 m
  • b) 1050 m
  • c)1280 m
  • d)1560 m
Q.17
The frequency of carries wave emitted from L - C oscillator of 10 μ H inductance and1 nF capacitor is .
  • a) 1592 KHz
  • b) 1592 Hz
  • c) 1592 MHz
  • d) 159.2 Hz
Q.18
If the band width is 1.6×1012Hz , how many communication channels can be obtainedwith 16 KHz band width radio signal ?
  • a) 1015
  • b) 1011
  • c)1010
  • d)108
Q.19
A transmitter transmit a power of 10 kw when modulation is 50%. What is the powerof carrier wave ?
  • a)12 KW
  • b) 7.0 KW
  • c)8.89 KW
  • d)5.0 KW
Q.20
A T.V. tower has a height 200 m. By how much the height of tower be increased totriple its coverage range ?
  • a)1600 m
  • b)800 m
  • c)1800 m
  • d)600 m
Q.21
The transmission of audio signal in radio broadcasting is type.
  • a) ASK
  • b) FSK
  • c) AM
  • d) FM
Q.22
Transmission loss per km in the optical fibre,used presently is,
  • a)20 dB
  • b) 2 dB
  • c)0.2 dB
  • d)0.02 dB
Q.23
In satellite communication 6 GHz frequency is used for and 4 GHz frequencyis used for
  • a)uplink, down link
  • b)down link, up link
  • c)modulation, demodulation
  • d)demodulation, modulation
Q.24
If a radio receiver amplifier all the signal frequencies equally well, it is said to have high
  • a) fidelity
  • b)distortion
  • c)sensibility
  • d) sensitivity
Q.25
In frequency modulation
  • a) the amplitude of modulated wave varies as frequency of carrier wave.
  • b) the frequency of modulated wave varies as amplitude of modulating wave.
  • c) The amplitude of modulated wave varies as amplitude of carrier wave.
  • d) The frequency of modulated wave varies as frequency of modulating wave.
Q.26
When electromagnetic waves enter the ionized layer of ionosphere, the relative permittingof the ionized layer
  • a)remain constant
  • b) appears to decrease
  • c)appears to increase
  • d)changes randomly
Q.27
For 100% modulation, What is the value of minimum amplitude Emin of the modulatedwave ?
  • a)Zero
  • b)1
  • c)2
  • d)3
Q.28
The velocity of e.m. waves in a medium is 2.5×108 m/s . what is the dielectric constantof the medium ?
  • a)1.2
  • b)1.44
  • c)0.69
  • d)1.6
Q.29
The condition under which a microwave oven heats up a food item containing water molecules most efficiently is … [ NEET 2013]
  • a) The frequency of the microwaves must match the resonant frequency of the water molecules
  • b) The frequency of the microwaves has no relation with natural frequency of water molecules
  • c) Microwaves are heat waves, so always produce heating
  • d) Infra-red waves produce heating in a microwave oven
Q.30
A radiation of energy E falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (C = Velocity of light) …[ NEET 2015]
  • a) E/C2
  • b) E/C
  • c) 2E/C
  • d) 2E/C2
0 h : 0 m : 1 s