A plane electromagnetic wave is propagating along the direction i ^ + j ^ 2 , with its polarization along the direction k . ^ The correct form of the magnetic field of the wave would be (here B 0 is an appropriate constant):

B 0 i ^ - j ^ 2 c o s ω t - k i ^ + j ^ 2

B 0 j ^ - i ^ 2 c o s ω t + k i ^ + j ^ 2

B 0 k ^ c o s ω t - k i ^ + j ^ 2

B 0 i ^ + j ^ 2 c o s ω t - k i ^ + j ^ 2

Match List – I with List – II . List – I List – II (a) 10 km height over earth's surface (i) Thermosphere (b) 70 km height over earth's surface (ii) Mesosphere (c) 180 km height over earth's surface (iii) Stratosphere (d) 270 km height over earth's surface (iv) Troposphere

( a )-( iv ), ( b )-( iii ), ( c )-( ii ), ( d )-( i )

( a )-( i ), ( b )-( iv ), ( c )-( iii ), ( d )-( ii )

( a )-( iii ), ( b )-( ii ), ( c )-( i ), ( d )-( iv )

( a )-( ii ), ( b )-( i ), ( c )-( iv ), ( d )-( iii )

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Long range radio transmission is possible when the radiowaves are reflected from the ionosphere. For this to happen the frequency of the radiowaves must be in the range :

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Important Questions on Communication Systems

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

The frequency suitable for beyond-the-horizon communication using sky waves is

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

The physical sizes of the transmitter and receiver antenna in a communication system are:

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

The maximum line-of-sight distance undefined between the transmitting antenna of height undefined and receiving antenna of height undefined in undefined communication is undefined radius of the earth)

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

The waves used for line of sight communication are

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

To double the covering range of a TV transmitting tower, its height should be multiplied by:

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

The waves suitable for transmission of radio signals are

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

A plane electromagnetic wave is propagating along the direction

\frac{\hat{i} + \hat{j}}{\sqrt{2}},

with its polarization along the direction

\hat{k .}

The correct form of the magnetic field of the wave would be (here

B_{0}

is an appropriate constant):

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

What should be the height of transmitting antenna and the population covered if the television telecast is to cover a radius of

150 km ?

The average population density around the tower is

2000 {km}^{- 2}

and the value of

R_{e} = 6.5 \times 10^{6} m .

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

A transmitting antenna at the top of a tower has a height $32 m$ and the height of the receiving antenna is $50 m$ . What is the maximum distance between them for satisfactory communication in line of sight (LOS) mode?

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

Long-range radio transmission is possible when the radio waves are reflected from the ionosphere. For this to happen the frequency of the radio waves must be in the range:

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

Match List

- I

with List

- II .

	List $- I$		List $- II$
(a)	$10 km$ height over earth's surface	(i)	Thermosphere
(b)	$70 km$ height over earth's surface	(ii)	Mesosphere
(c)	$180 km$ height over earth's surface	(iii)	Stratosphere
(d)	$270 km$ height over earth's surface	(iv)	Troposphere

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

A TV transmission tower has a height of

140 m

and the height of the receiving antenna is

40 m .

What is the maximum distance upto which signals can be broadcasted from this tower in LOS (Line of Sight) mode? (Given: radius of earth

= 6.4 \times 10^{6} m) .

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

Choose the incorrect statement(s):

(i) Skywave communication takes place at frequency above approximately $30 MHz$ .

(ii) Amplitude modulated (AM) radio communication is mostly done by ground wave propagation.

(iii) $F$ layer of ionosphere is mostly responsible for skywave propagation.

(iv) Bandwidth required for transmission of video signal is generally more than audio signal.

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

For efficient transmission and reception, the height of antenna should be atleast

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

A TV transmitting antenna is

81 m

tall. It has half-power, beam-width of

10

degrees, If the receiving antenna is at the ground level, the service area covered by the transmitter is determined by

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

High frequency waves follow:

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

Which of the following frequencies will be suitable for beyond the horizon communication using sky waves?

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

In a line of sight radio communication, a distance of about

50 km

is kept between the transmitting and receiving antennas. If the height of the receiving antenna is

70 m,

then the minimum height of the transmitting antenna should be: (Radius of the Earth

= 6.4 \times 10^{6} m

)

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

A plane electromagnetic wave of wavelength

λ

has an intensity

I

. It is propagating along the positive

Y -

direction. The allowed expressions for the electric and magnetic fields are given by:

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Physics>Modern Physics>Communication Systems>Propagation of Electromagnetic Waves in Atmosphere

In a communication system operating at wavelength

800 n m,

only one percent of source frequency is available as signal bandwidth. The number of channels accommodated for transmitting

T V

signals of band width

6 M H z

are (Take velocity of light

c = 3 \times 10^{8} m / s, h = 6.6 \times 10^{- 34} J - s

)

Long range radio transmission is possible when the radiowaves are reflected from the ionosphere. For this to happen the frequency of the radiowaves must be in the range :

Important Questions on Communication Systems

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