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Physics M.C.Q (1 Marks)

Electromagnetic Waves and Communication System · Maharashtra Board STD 11 (MSBSHSE - Semi English Medium). 52 questions.

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M.C.Q (1 Marks)

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52 questions · auto-graded multiple-choice test.

MCQ 11 Mark
If a TV telecast is to cover a radius of 640 km, what should be the height of transmitting antenna?
  • ✓
    32000 m
  • B
    53000 m
  • C
    42000 m
  • D
    55000 m
Answer
Correct option: A.
32000 m
32000 m
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MCQ 21 Mark
The waves used by artificial satellites for communication purposes are
  • ✓
    Microwave
  • B
    AM radio waves
  • C
    FM radio waves
  • D
    X-rays
Answer
Correct option: A.
Microwave
Microwave
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MCQ 31 Mark
The maximum distance upto which TV transmission from a TV tower of height h can be received is proportional to
  • ✓
    $h \frac{1}{2}$
  • B
    $h$
  • C
    $h \frac{2}{3}$
  • D
    $h^2$
Answer
Correct option: A.
$h \frac{1}{2}$
$h \frac{1}{2}$
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MCQ 41 Mark
The direction of $EM$ wave is given by
  • ✓
    $\bar{E} \times B$
  • B
    $\bar{E} . B$
  • C
    along $\bar{E}$
  • D
    along $B$
Answer
Correct option: A.
$\bar{E} \times B$
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MCQ 51 Mark
How does the frequency of a beam of ultraviolet light change when it travels from air into glass?
  • A
    depends on the values of p and e
  • B
    increases
  • C
    decreases
  • ✓
    remains same
Answer
Correct option: D.
remains same
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MCQ 71 Mark
The EM wave emitted by the Sun and responsible for heating the Earth’s atmosphere due to greenhouse effect is
  • ✓
    Infra-red radiation
  • B
    X ray
  • C
    Microwave
  • D
    Visible light
Answer
Correct option: A.
Infra-red radiation
Infra-red radiation
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MCQ 81 Mark
In frequency modulated wave
  • ✓
    frequency varies with time
  • B
    both frequency and amplitude vary with time
  • C
    amplitude varies with time
  • D
    both frequency and amplitude are constant.
Answer
Correct option: A.
frequency varies with time
(a) : In frequency modulated wave frequency varies with time.
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MCQ 91 Mark
A layer of atmosphere that reflects medium frequency radio waves which is ineffective during night is
  • A
    F layer
  • ✓
    E layer
  • C
    Stratosphere
  • D
    Thermosphere
Answer
Correct option: B.
E layer
(b) : E-layer is at a virtual height of $100 km$ from the surface of earth. This layer exists during day time but disappears at night. The critical frequency of this layer is about $4 MHz$ and reflects medium frequency radio waves $(300 KHz$ to $3 MHz$ ).
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MCQ 101 Mark
In amplitude modulation
  • A
    amplitude remains constant, but frequency changes.
  • B
    both amplitude and frequency do not change.
  • C
    both amplitude and frequency change.
  • ✓
    amplitude of the carrier wave changes according to information signal.
Answer
Correct option: D.
amplitude of the carrier wave changes according to information signal.
(d) : In amplitude modulation, amplitude of the carrier wave changes according to information signal.
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MCQ 111 Mark
In communication system, the process of superimposing a low frequency signal on a high frequency wave is known as
  • A
    Repeater
  • B
    Attenuation
  • ✓
    Modulation
  • D
    Demodulation
Answer
Correct option: C.
Modulation
(c) : Modulation is a process of superimposing a low frequency signal on a high frequency wave.
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MCQ 121 Mark
The maximum frequency of transmitted radio waves above which the radio waves are no longer reflected back by ionosphere is ( $N=$ maximum electron density of ionosphere, $g=$ acceleration due to gravity)
  • A
    $g N$
  • B
    $g N^2$
  • ✓
    $g \sqrt{N}$
  • D
    $g^2 N^2$
Answer
Correct option: C.
$g \sqrt{N}$
(c) : Maximum frequency of transmitted radio waves, above which the radio waves are no longer reflected back by ionosphere is called critical frequency which is given by $f_c=g \sqrt{N}$.
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MCQ 131 Mark
The process of regaining of information from carrier wave at the receiver is termed as
  • ✓
    demodulation
  • B
    modulation
  • C
    attenuation
  • D
    amplification
Answer
Correct option: A.
demodulation
(a) : It is reverse process of modulation.
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MCQ 141 Mark
For efficient radiation and reception of signal with wavelength λ, the transmitting antennas would have length comparable to ……………….
  • ✓
    $\lambda$ of frequency used
  • B
    $\lambda / 2$ of frequency used
  • C
    $\lambda / 3$ of frequency used
  • D
    $\lambda / 4$ of frequency used
Answer
Correct option: A.
$\lambda$ of frequency used
$\lambda$ of frequency used
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MCQ 151 Mark
The power radiated by linear antenna of length 7’ is proportional to (A = wavelength)
  • A
    $\frac{\lambda}{l}$
  • B
    $\left(\frac{\lambda}{l}\right)^2$
  • C
    $\frac{l}{\lambda}$
  • ✓
    $\left(\frac{l}{\lambda}\right)^2$
Answer
Correct option: D.
$\left(\frac{l}{\lambda}\right)^2$
$\left(\frac{l}{\lambda}\right)^2$
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MCQ 161 Mark
In a communication system, noise is most likely to affect the signal ………..
  • A
    at the transmitter
  • ✓
    in the transmission medium
  • C
    in the information source
  • D
    at the destination
Answer
Correct option: B.
in the transmission medium
in the transmission medium
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MCQ 171 Mark
If $‘h_t \ ‘$ and $‘h_r \ ’$ are height of transmitting and receiving antennae and $‘R \ ’$ is radius of the earth, the range of space wave is
  • A
    $\sqrt{2 R}\left(h_t+h_r\right)$
  • B
    $2R \sqrt {(h_t + h_r)}$
  • C
    $\sqrt {2R(h_t + h_r)}$
  • ✓
    $\sqrt{2 R}\left(\sqrt{ } h_{ t }+\sqrt{ } h _{ r }\right)$
Answer
Correct option: D.
$\sqrt{2 R}\left(\sqrt{ } h_{ t }+\sqrt{ } h _{ r }\right)$
$\sqrt{2 R}\left(\sqrt{ } h_{ t }+\sqrt{ } h _{ r }\right)$
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MCQ 181 Mark
Transmission lines start radiating
  • A
    at low frequencies
  • ✓
    at high frequencies.
  • C
    at both high and low frequencies.
  • D
    none of the above.
Answer
Correct option: B.
at high frequencies.
at high frequencies.
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MCQ 191 Mark
Space wave travels through …………………
  • A
    ionosphere
  • B
    mesosphere
  • ✓
    troposphere
  • D
    stratosphere
Answer
Correct option: C.
troposphere
troposphere
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MCQ 201 Mark
An antenna behaves as resonant circuit only when its length is ……………
  • A
    $\lambda / 2$
  • B
    $\lambda / 4$
  • C
    $\lambda$
  • ✓
    n $\lambda / 2$
Answer
Correct option: D.
n $\lambda / 2$
n $\lambda / 2$
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MCQ 211 Mark
The portion of the atmosphere closest to the earth’s surface is ……………
  • ✓
    troposphere
  • B
    stratosphere
  • C
    mesosphere
  • D
    ionosphere
Answer
Correct option: A.
troposphere
troposphere
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MCQ 221 Mark
What determines the absorption of radio waves by the atmosphere?
  • ✓
    Frequency
  • B
    Polarisation
  • C
    Interference
  • D
    Distance of receiver
Answer
Correct option: A.
Frequency
Frequency
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MCQ 231 Mark
Modem communication systems consist of
  • A
    electronic systems
  • B
    electrical system
  • C
    optical system
  • ✓
    all of these
Answer
Correct option: D.
all of these
all of these
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MCQ 241 Mark
The ozone layer in the atmosphere absorbs
  • A
    only the radio waves.
  • B
    only the visible light.
  • C
    only the y rays.
  • ✓
    X-rays and ultraviolet rays.
Answer
Correct option: D.
X-rays and ultraviolet rays.
X-rays and ultraviolet rays.
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MCQ 251 Mark
Line of sight propagation is also called as ……………. propagation.
  • A
    sky wave
  • B
    ground wave
  • C
    sound wave
  • ✓
    space wave
Answer
Correct option: D.
space wave
space wave
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MCQ 261 Mark
The message fed to the transmitter are generally
  • A
    radio signals
  • ✓
    audio signals
  • C
    both (A) and (B)
  • D
    optical signals
Answer
Correct option: B.
audio signals
audio signals
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MCQ 271 Mark
Communication is the process of
  • A
    keeping in touch.
  • ✓
    exchanging information.
  • C
    broadcasting
  • D
    entertainment
Answer
Correct option: B.
exchanging information.
exchanging information.
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MCQ 281 Mark
The reflected waves from the ionosphere are
  • A
    ground waves.
  • ✓
    sky waves.
  • C
    space waves.
  • D
    very high frequency waves.
Answer
Correct option: B.
sky waves.
sky waves.
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MCQ 291 Mark
Ionosphere mainly consists of
  • ✓
    positive ions and electrons
  • B
    water vapour and smoke
  • C
    ozone layer
  • D
    dust particles
Answer
Correct option: A.
positive ions and electrons
positive ions and electrons
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MCQ 301 Mark
Range of can be increased by
  • ✓
    increasing the heights of transmitting and receiving antennas.
  • B
    decreasing the heights of transmitting and receiving antennas.
  • C
    increasing height of transmitting antenna and decreasing the height of receiving antenna.
  • D
    increasing height of receiving antenna only.
Answer
Correct option: A.
increasing the heights of transmitting and receiving antennas.
increasing the heights of transmitting and receiving antennas.
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MCQ 311 Mark
The process of regaining of information from carries wave at the receiver is called
  • A
    modulation
  • B
    transmission
  • C
    propagation
  • ✓
    demodulation
Answer
Correct option: D.
demodulation
demodulation
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MCQ 321 Mark
A microphone which converts sound into electrical signal is an example of .
  • A
    a thermistor
  • B
    a rectifier
  • C
    a modulator
  • ✓
    an electrical transducer
Answer
Correct option: D.
an electrical transducer
an electrical transducer
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MCQ 331 Mark
A device that converts one form of energy into another form is termed as ……………
  • ✓
    transducer
  • B
    transmitter
  • C
    amplifier
  • D
    receiver
Answer
Correct option: A.
transducer
transducer
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MCQ 341 Mark
The process of superimposing a low frequency signal on a high frequency wave is …………….
  • A
    detection
  • B
    mixing
  • ✓
    modulation
  • D
    attenuation
Answer
Correct option: C.
modulation
modulation
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MCQ 351 Mark
The process of changing some characteristics of a carrier wave in accordance with the incoming signal is called …………..
  • A
    amplification
  • ✓
    modulation
  • C
    rectification
  • D
    demodulation
Answer
Correct option: B.
modulation
modulation
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MCQ 361 Mark
Basic components of a transmitter are ……………..
  • A
    message signal generator and antenna
  • B
    modulator and antenna
  • C
    signal generator and modulator
  • ✓
    message signal generator, modulator and antenna
Answer
Correct option: D.
message signal generator, modulator and antenna
message signal generator, modulator and antenna
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MCQ 371 Mark
When radio waves from transmitting antenna reach the receiving antenna directly or after reflection in the ionosphere, the wave propagation is called ………………
  • A
    ground wave propagation
  • B
    space wave propagation
  • ✓
    sky wave propagation
  • D
    satellite propagation
Answer
Correct option: C.
sky wave propagation
sky wave propagation
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MCQ 381 Mark
The electronic transition in atom produces
  • A
    ultra violet light
  • ✓
    visible light
  • C
    infra-red rays
  • D
    microwaves
Answer
Correct option: B.
visible light
visible light
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MCQ 391 Mark
The nuclei of atoms of radioactive elements produce ……………
  • A
    X-rays
  • ✓
    $\gamma$-rays
  • C
    microwaves
  • D
    ultra-violet rays
Answer
Correct option: B.
$\gamma$-rays
$\gamma$-rays
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MCQ 401 Mark
The correct sequence of descending order of wavelength values of the given radiation source is …………..
  • ✓
    radio waves, microwaves, infra-red, $\gamma$ - rays
  • B
    $\gamma$-rays, infra-red, radio waves, microwaves
  • C
    Infra-red, radio waves, microwaves, $\gamma^{-}$rays
  • D
    microwaves, $\gamma$-rays, infra-red, radio waves
Answer
Correct option: A.
radio waves, microwaves, infra-red, $\gamma$ - rays
radio waves, microwaves, infra-red, $\gamma$ - rays
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MCQ 411 Mark
The part of electromagnetic spectrum used in operating radar is ……………
  • A
    y-rays
  • B
    visible rays
  • C
    infra-red rays
  • ✓
    microwaves
Answer
Correct option: D.
microwaves
microwaves
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MCQ 421 Mark
Out of the X-rays, microwaves, ultra-violet rays, the shortest frequency wave is …………
  • A
    X-rays
  • ✓
    microwaves
  • C
    ultra-violet rays
  • D
    $\gamma$-rays
Answer
Correct option: B.
microwaves
microwaves
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MCQ 431 Mark
If $E$ is an electric field and $\vec{B}$ is the magnetic induction, then the energy flow per unit area per unit time in an electromagnetic field is given by
  • ✓
    $\frac{1}{\mu_0} \vec{E} \times \vec{B}$
  • B
    $\vec{E} \cdot \vec{B}$
  • C
    $E ^2+ B ^2$
  • D
    $\frac{E}{B}$
Answer
Correct option: A.
$\frac{1}{\mu_0} \vec{E} \times \vec{B}$
$\frac{1}{\mu_0} \vec{E} \times \vec{B}$
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MCQ 441 Mark
Which of the following electromagnetic wave has least wavelength?
  • ✓
    Gamma rays
  • B
    X- rays
  • C
    Radio waves
  • D
    microwaves
Answer
Correct option: A.
Gamma rays
Gamma rays
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MCQ 451 Mark
Radio waves do not penetrate in the band of
  • ✓
    ionosphere
  • B
    mesosphere
  • C
    troposphere
  • D
    stratosphere
Answer
Correct option: A.
ionosphere
ionosphere
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MCQ 461 Mark
Which of the following electromagnetic waves have the longest wavelength?
  • A
    heat waves
  • B
    light waves
  • ✓
    radio waves
  • D
    microwaves
Answer
Correct option: C.
radio waves
radio waves
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MCQ 471 Mark
In an electromagnetic wave, the direction of the magnetic induction $\vec{B}$ is
  • A
    parallel to the electric field $\vec{E}$.
  • ✓
    perpendicular to the electric field $\vec{E}$.
  • C
    antiparallel to the pointing vector $\vec{S}$.
  • D
    random
Answer
Correct option: B.
perpendicular to the electric field $\vec{E}$.
perpendicular to the electric field $\vec{E}$.
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MCQ 481 Mark
The electromagnetic waves do not transport.
  • A
    energy
  • ✓
    charge
  • C
    momentum
  • D
    pressure
Answer
Correct option: B.
charge
charge
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MCQ 491 Mark
According to Maxwell’s equation the velocity of light in any medium is expressed as
  • A
    $\frac{1}{\sqrt{\mu_0 \varepsilon_0}}$
  • ✓
    $\frac{22}{\sqrt{\mu \varepsilon}}$
  • C
    $\sqrt{\frac{\mu}{\varepsilon}}$
  • D
    $\sqrt{\frac{\mu_0}{\varepsilon}}$
Answer
Correct option: B.
$\frac{22}{\sqrt{\mu \varepsilon}}$
$\frac{22}{\sqrt{\mu \varepsilon}}$
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MCQ 501 Mark
The unit of expression $\mu_0 0 \varepsilon_0$ is
  • A
    $m / s$
  • B
    $m ^2 / s ^2$
  • ✓
    $s ^2 / m ^2$
  • D
    $s / m$
Answer
Correct option: C.
$s ^2 / m ^2$
$s ^2 / m ^2$
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MCQ 511 Mark
If $\vec{E}$ and $\vec{B}$ are the electric and magnetic field vectors of e.m. waves, then the direction of propagation of e.m. direction of wave is along the
  • A
    $\vec{E}$
  • B
    $\vec{B}$
  • ✓
    $\vec{E} \times \vec{B}$
  • D
    $\vec{E} \cdot \vec{B}$
Answer
Correct option: C.
$\vec{E} \times \vec{B}$
$\vec{E} \times \vec{B}$
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MCQ 521 Mark
Which of the following type of radiations are radiated by an oscillating electric charge?
  • A
    Electric
  • B
    Magnetic
  • C
    Thermoelectric
  • ✓
    Electromagnetic
Answer
Correct option: D.
Electromagnetic
Electromagnetic
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