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Electromagnetic Wave And Communication Mcq
Quiz 3
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Q.1
The theory of electromagnetic waves predicted by Maxwell in 1888 was confirmed experimently first be
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a) Maxwell
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b) Hertz
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c)Marconi
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d)J.C.Bose
Explanation
Answer: (b)
Q.2
X-ray are produced by jumping of
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a) electrons from lower to higher energy orbit of atom
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b) electrons from higher to lower energy orbit of atom
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c)protons from lower to higher energy orbit of nucleus
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d)proton from higherr to lower energy orbit of nucleus
Explanation
Answer:(b)
Q.3
A radiowave has a maximum magnetic field induction of 10-4 T on arrival at a receving antenna. The maximum electric field intenisty of such wave is
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a) zero
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b) 3 ×104 V/m
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c) 5.8 × 10-9 V/m
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d) 3.3 × 10-13 V/m
Explanation
Answer: (b)
Q.4
The earth is surrounded by atmosphere up to a height of about
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a)200 km
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b) 400 km
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c)500 km
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d)600 km
Explanation
Answer: (b)
Q.5
Displacement current flows
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a) in between capacitor plates and wires of circuit
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b) in between capacitor plates only
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c)in resistance only
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d)depends on e.m.f of cell and value of R
Explanation
Answer: (b)
Q.6
Which of the following type of radiations are radiated by an oscillating electric charge
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a) electric
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b) magnetic
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c)thermoelectric
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d)electromagentic
Explanation
Answer:(d)
Q.7
The small ozone layer on top of the atmosphere is crucial for human survival because it
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a) has ions
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b) reflects raddio signals
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c) reflects UV rays
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d) reflects IR rays
Explanation
Answer: (c)
Q.8
In electromagnetic wave, the average energy density is associated to
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a)electric field only
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b) magnetic field only
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c)equally with electric and magnetic field
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d)average energy density is zzzero
Explanation
Answer: (c)
Q.9
In an electromagentic wave, the average energy density associated with magnetic field is
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a) LIo2 /2
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b) B2/ 2µo
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c)µoB2 / 2
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d)µo / 2B2
Explanation
Answer: (b)
Q.10
If E is an electric field and B is the magnetic induction, then the energy flow per unit area per unit time in an electromagnetic field is given by
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a) E × B
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b) E . B
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c)E2 + B2
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d)E/B
Explanation
Answer:(a)
Q.11
In an electromagnetic wave, the direction of the magnetic induction B is
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a) Parallel to the lectric field E
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b) Perpendicular to the lectic field E
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c) antiparallel to the polynting vector S
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d) radom
Explanation
Answer: (b)
Q.12
In a plane electromagentic wave propogating in space has an electric field of amlitude 9×103 V/m, then the amplitude of magnetic field is
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a)2.7 × 1012 T
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b) 9.0 × 10-3 T
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c)3.0 × 10-4 T
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d)3.0 × 10-5 T
Explanation
Answer: (d)
Q.13
A free electron is placed in the path of a plane electromagnetic wave, it will start moving along
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a) centre of earthh
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b) equator of earth
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c)magnetic field
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d)electric field
Explanation
Answer: (d)
Q.14
In an electromagnetic wave the average energy density associated with electric field is
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a) CV2 /2
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b) εo2 / 2E
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c)Q2/ 2C
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d)εoE2 / 2
Explanation
Answer:(d)
Q.15
Ozone blocks the radiations of wave length
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a) less than 3 × 10-7 m
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b) equal to 3 × 10-7 m
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c) more than 3 × 10-7 m
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d) all of these
Explanation
Answer: (a)
Q.16
The temperature variation in the region of stratosphere lies from
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a)290 K to 220 K
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b) 220 K to 280 K
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c)280 K to 180 K
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d)180 K to 700 K
Explanation
Answer: (b)
Q.17
Long distance radio broadcasts use short wave band because
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a) they have short wavelength
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b) they scatter less
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c)they are reflected by ionosphere
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d)they have more energy to propogate
Explanation
Answer: (c)
Q.18
The frequency from 3 to 30 MHz is known as
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a) audio band
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b) medium frequency band
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c)high frequency band
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d)very high frequecy band
Explanation
Answer:(c)
Q.19
The temperature variation in the region of stratosphere lies from
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a) 290 K to 220 K
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b) 220 K to 280 K
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c) 280 K to 180 K
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d) 180 K to 700 K
Explanation
Answer: (b)
Q.20
The electromagnetic waves
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a)travel with the speed of sound
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b) travel with the same speed in all medium
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c)travel in free space with the speed of light
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d)do not travel through medium
Explanation
Answer: (c)
Q.21
Which of the following electromagnetic waves have the longest wavelength
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a) heat waves
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b) light waves
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c)radio waves
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d)microwaves
Explanation
Answer: (c)
Q.22
Which of the following is of shortest wave length
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a) X-rays
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b) γ-rays
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c)microwaves
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d)radiowaves
Explanation
Answer:(b)
Q.23
The displacement current flows in a dielectric of capacitor, when potential difference across its plates
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c) becomes zero
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a) is increasing/ decreasing with tine
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b) is decreasing with times only
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d) becomes infinite
Explanation
Answer: (a)
Q.24
The nature of electric field in the region between the two plates of capacitor, while charging is
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a)always constant
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b) varying
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c)depends on value of C and R
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d)depends on e.m.f of battery
Explanation
Answer: (b)
Q.25
An electric field E and magnetic field B exists in a region. If these field are not perpendicular to each other, then the electromagnetic wave
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a) will not pass through the region
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b) will pass through region
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c)may pass through the region
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d)nothing is definite
Explanation
Answer: (c)
Q.26
The wavelength of ultraviolet rays is of the order of
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a) 10-3 m
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b) 10-6 m
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c)10-8 m
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d)between 'b' and 'c'
Explanation
Answer:(d)
Q.27
The energy of X-ray photon is 3.3 ×10-16 J its frequency is
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a) 2 × 1019 Hz
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b) 5 × 1018 Hz
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c) 5 × 1017 Hz
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d) 5 × 1016 Hz
Explanation
Answer: (c)
Q.28
The penitration power of X-ray increases with the increase in its
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a)velocity
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b) intensity
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c)frequency
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d)wave length
Explanation
Answer: (c)
Q.29
The voltage applied across an X-ray tube is nearly equal to
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a) 10 V
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b) 100 V
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c)1000 V
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d)10,000 V
Explanation
Answer: (d)
Q.30
The speed of electromagnetic wave is same for
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a) odd frequencies
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b) all frequencies
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c)all intensities
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d)even frequencies
Explanation
Answer:(c)
0 h : 0 m : 1 s
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