An electromagnetic wave going through vaccum is described by E=o E sin(kx- ω t).Which of the following is independent of the wavelength?
33%
a) ω
33%
b)k/ ω
33%
c) k ω
0%
d)k
Q.2.
Which of the following have zero average value in a plane electromagnetic wave?
17%
a) Electric energy
17%
b) Magnetic energy
50%
c) Electric field
17%
d)None of these.
Q.3.
If the relative permeability and dielectric constant of a given medium are equal to µr and K respectively, then the refractive index of the medium is equalto__________
50%
a) √(µr) K
33%
b) √(µr) Eo
17%
c) √(µo) Eo
0%
d) √(µr)/ K
Q.4.
Astraonomers have found that electromagnetic waves of wavelength 21cm arecontinuously reaching the Earth’s surface . Calculate the frequency of this radiation.(c=3 ×108m/s)
40%
a)14.28 GHz
40%
b)1.428 kHz
0%
c)1.428 MHz
20%
d)1.428 GHz
Q.5.
Electric field in an electromagnetic wave is given by E=50 sinω(t-x/c) NC-1 .Intensity of this wave is ___________ Wm-2
0%
a) 50
40%
b)1.1×108
20%
c)3.3
40%
d)5.5×10-19
Q.6.
The amplitude of the electric field in a parallel beam of light of intensity 2.0Wm-2is _______
20%
a) 38.8NC-1
20%
b) 19.4NC-1
20%
c)9.7NC-1
40%
d)None of these.
Q.7.
Speed of electromagnetic wave is the same
0%
a) for all wavelengths
40%
b) in all media
40%
c) for all intensities
20%
d) for all frequencies
Q.8.
The maximum electric field in a plane electromagnetic wave is 900NC-1 . The waveis going in the x direction and the electric field is in the y direction. The maximummagnetic field in the wave is ____________T
0%
a)3×10-8
67%
b) 3×10-6
17%
c)27×10-6
17%
d)27×1010
Q.9.
Electromagnetic waves are produced by
0%
a)a static charge
0%
b)a moving charge
100%
c)an accelerating charge
0%
d)chargeless particles
Q.10.
Maxwells equations are derived from the laws of___________
0%
a)electricity
20%
b) magnetism
60%
c)both electricity and magnetism
20%
d)mechanics
Q.11.
Which of the following electromagnetic waves has the longest wavelength?
60%
a) Radio waves
20%
b) Infrared radiations
20%
c) x rays
0%
d) visible rays
Q.12.
Which of the following electromagnetic waves has the highest frequency?
0%
a)radio waves
20%
b)micro waves
80%
c) γ rays
0%
d)x rays
Q.13.
The maximum value of E in an electromagnetic waves in air is equal to 6.0×10-4 Vm . The maximum value of B is ____________
17%
a) 1.8×105 T
17%
b) 2×104 T
33%
c)2×10-12 T
33%
d)1.8×1013 T
Q.14.
Dimensional formula of intensity of radiation is _____________
20%
a) M1L2T-2
0%
b) M1L0T-2
40%
c)M1L1T-3
40%
d)M1L0T-3
Q.15.
The frequency of an electromagnetic wave in free space is 3MHz. When it passesthrough a medium of relative permeability εr=4.0 , then its frequency
0%
a) becomes half
40%
b) become doubled
40%
c) remain same
20%
d) become √2 times
Q.16.
The frequency of electromagnetic wave having wavelength 25mm is _________ Hz
20%
a)1.2 ×1010
20%
b) 7.5 ×105
40%
c)1.2 ×108
20%
d)7.5 ×106
Q.17.
Unit of energy density of electromagnetic wave is _________
60%
a)Jm-3
0%
b)Jm-2
20%
c)wm-2
20%
d)None of these
Q.18.
What is the ratio of velocities of light rays of wavelengths 40000 Å and 80000 Å in vaccum ?
20%
a)1:2
40%
b) 1:1
0%
c)2:1
40%
d)cannot be determined
Q.19.
Which of the following rays are not electromagnetic waves?
0%
a) α rays
20%
b) β rays
0%
c) γ rays
80%
d) heat rays
Q.20.
A plane electromagnetic wave of frequency 25MHz travels in free space along thex direction. At a particular point in space and time E=6.3jVm-1 then Bat this point is__________
20%
a)2.1 × 10-8 i T
0%
b)2.1 × 10-8 k T
40%
c)1.89× 109 k T
40%
d)2.52× 10-7 k T
Q.21.
The magnetic field in a plane electromagnetic wave is given By=2×10-7 sin ( 0.5×103x + 1.5×1011t) T
20%
a) Ex=60 sin ( 0.5×103x + 1.5×1011t) V/m
40%
b) Ez=60 sin ( 0.5×103x + 1.5×1011t) V/m
20%
c) Ex=60 sin ( 1.5×103x + 0.5×1011t) V/m
20%
d) Ex=60×1015 sin ( 1.5×103x + 0.5×1011t) V/m
Q.22.
Light with an energy flux of w/m3 falls on a non-reflecting surface atnormal to surface. If the surface has an area of 20m2 . The average force exertedon the surface during 30 minutes is________
20%
a)6.48×105 N
20%
b)3.60×102 N
40%
c)1.2×10-6 N
20%
d)2.16×10-3N
Q.23.
Energy density of an electromagnetic wave of intensity 0.02 Wm-2 is _______
40%
a) 6.67×10-11 Jm-3
0%
b)6×106 Jm-3
40%
c)1.5×1010 Jm-3
20%
d)none of the above
Q.24.
The waves used in communication are generally called
0%
a)γ ray
0%
b) α ray
20%
c) microwaves
80%
d)radiowave
Q.25.
For an electromagnetic wave, the phase difference between vectors E and B (faraway from the source)
20%
a) 0
20%
b) π /2
20%
c) π
40%
d) 3π/2
Q.26.
The electric and magnetic field of an electromagnetic wave are
40%
a) in phase and perpendicular to each other
20%
b)in phase and parallel to each other
20%
c) in opposite phase and perpendicular to each other
20%
d) in opposite phase and parallel to each other
Q.27.
Unit of µo C is same as that of
20%
a)current
20%
b)resistance
0%
c) electric charge
60%
d) velocity
Q.28.
If the direction of magnetic field B at some instant is along +ve Z direction and the electromagnetic wave is propagating along +ve X direction, then the direction of electric field E at that instant is_________
0%
a) along -ve Y direction
40%
b) along +ve Y direction
40%
c) along +ve X direction
20%
d) along -ve X direction
Q.29.
The velocity of light in vaccum can be changed by changing____
20%
a) frequency
0%
b)wavelength
40%
c) amplitude
40%
d) none of these
Q.30.
Which of the Following is not a component of communication System ?
0%
a) Transmitter
20%
b) Transmission channel
60%
c) Noise
20%
d) Receiver
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