If E and B are the electric and magnetic field vectors of e.m. waves then the direction of propogation of e.m waves is along the direction of
0%
a) E
0%
b) B
100%
c) E × B
0%
d) none of these
Q.2.
In a plane e.m wave, the electric field oscillattes sinusoidally at frequency of 2 × 1010 Hz and amplitude 48 V/m. The wavelength of the wave is
0%
a)24 × 10-1 m
75%
b) 1.5 × 10-2 m
0%
c)4.16 × 108 m
25%
d)3 ×10-8 m
Q.3.
In the above question the amplitude of the oscillating magnetic field is
0%
a) 48 T
25%
b) 14.4 × 1010 T
25%
c)24 × 10-10 T
50%
d)1.6 × 10-7 T
Q.4.
A plane electromagnetic wave is incident on a meterial surfcae. If the wave delivers momentum ρ and energy E, then
25%
a) ρ=0, E=0
25%
b) ρ ≠ 0, E ≠ 0
50%
c)ρ ≠ 0, E=0
0%
d)ρ=0, E ≠ 0
Q.5.
If the earth did not have atmosphere, its surface temperature on a day time would be
50%
a) higher
25%
b) lower
25%
c) same as now
0%
d) not sure
Q.6.
The AM range of radio waves have frequency
50%
a)less than 30 MHz
25%
b) more than 30 MHz
25%
c)less than 20,000 Hz
0%
d)more than 20,000 Hz
Q.7.
Height 'h' of transmitting antenna when R is the radius of earth to have range 'd' is
25%
a) d2 / 2R
50%
b)√(2dR)
0%
c)2d2/R
25%
d)2R2 / d
Q.8.
A TV tower has a height of 100 m. How much population is covered by the TV broadcasrt if the average population density around the tower is 1000 km-2 ( radius of earth=6.37 × 106 m)
50%
a) 4 lakh
0%
b) 4 billion
0%
c)40,000
50%
d)40 lakh
Q.9.
Which of the following is better carrier of signals?
50%
a) radiowaves
0%
b) light waves
25%
c) micro waves
25%
d) ultrasonic waves
Q.10.
The minimum frequecny ν of continuous X-ray is related to the applied potential difference V as
75%
a)ν ∝ V
0%
b) ν ∝ V1/2
0%
c)ν ∝ V-3
25%
d)ν ∝ V4
Q.11.
Conduction current is
0%
a) continuous through out
25%
b) discontinuous in circuit with capacitors
50%
c)continuous wherever electric field chages
25%
d)continuous in every type of circuit
Q.12.
Ampere's circutl law holds good for
50%
a) conduction current
25%
b) dispalcement current
0%
c)both
25%
d)none of these
Q.13.
The energy of X-ray photon is 2200 eV. Its frequency would be
0%
a) 5.3 × 1016 Hz
75%
b) 5.3 × 1017 Hz
25%
c) 5.3 × 1018 Hz
0%
d) 5.3 × 1015 Hz
Q.14.
The amplitudes of electric and magnetic field related to each other are
50%
a)Eo=Bo
25%
b) Eo=cBo
0%
c)Eo=Bo/c
25%
d)Eo=c/Bo
Q.15.
At which of the following frequency / frequencies the communication will not be reliable for a receiver situated below horizon
50%
a) 100 kHz
25%
b) 1 MHz
25%
c)1 Ghz
0%
d)100 GHz
Q.16.
In short wave communication waves of which of the following frequencies will be rfeclected back by the ionosphereic layer, having electron density 1011 per m3?
50%
a) 2 Mhz
50%
b) 10 MHz
0%
c)12 MHz
0%
d)18 MHz
Q.17.
If µ1 and µ2 are the refractive indexes 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
25%
a) µ1 > µ2
0%
b) µ1 < µ2
75%
c) µ1=µ2
0%
d) none of the above
Q.18.
A laser beam is used for carrying out surgery beacuse it
50%
a)is highly monocharomatic
0%
b) is higly coherent
0%
c)is higly directional
50%
d)can be spherply focussed
Q.19.
The maximum distance upto which TV transmission from a TV tower of height h can be received is proportional to
50%
a)√h
25%
b) h
0%
c)h3/2
25%
d)h2
Q.20.
The attenuation in optical fibre is maily due to
0%
a) absorption
0%
b) scattering
0%
c)neither absorption nor scattering
100%
d)both (a) and (b)
Q.21.
Modulation is used to
25%
a) reduce the bandwidth used
25%
b) separate the transmissions of different users
50%
c)ensure that intelligence may be transmitted to long distance
0%
d)allow the use of practical antinnas
Q.22.
The process of super imposing signal frequency ( i.e. audio wave) on the carrier wave is known as
50%
a) transmission
25%
b) reception
25%
c) modulation
0%
d) detection
Q.23.
AM is used for broadcasting because
0%
a)it is more noise immune than other modulation systems
50%
b) it requires less transmitting power compared with other systems
50%
c)its use avoids receiver complexity
0%
d)no other modulation system can provide the necessary bandwidth
Q.24.
The impedance of a perfect conductor to e.m. waves is
25%
a) zero
0%
b) 1
50%
c)∞
25%
d)none of these
Q.25.
The area to be covered for TV telecast is doubled. Then the height of transmitting antenna ( TV tower) will have to be
25%
a) douled
50%
b) halved
0%
c)quadrupled
25%
d)kept uncharged
Q.26.
Crystal oscillator is preferred for the generation of carrier waves because of
50%
a) large output power
25%
b) larger amplification
0%
c) larger voltage gain
25%
d) better stability
Q.27.
What is the minimum number of geostationary satellites required for un interrupted global coverage?
20%
a)3
60%
b) 5
0%
c)7
20%
d)9
Q.28.
Frequencies in the UHF range normally propogated by means of
0%
a) ground waves
50%
b) sky waves
0%
c)surface waves
50%
d)space waves
Q.29.
In AM systems, complete information is conveyed by transmitting in
0%
a) carrier
25%
b) lower side band
25%
c)upper side band
50%
d)any of the two side bands
Q.30.
In an amplitude modulated wave for audio frequency of 500 cycles/second. the appropriate carrier frequency will be
50%
a) 50 cycles/s
0%
b) 1000 cycles/s
0%
c) 500 cyles/s
50%
d) 50000 cycles/s
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