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12th Standard Physics Communication Systems English Medium Free Online Test One Mark questions with Answer Key 2020 - 2021

12th Standard EM

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Physics

Time : 00:20:00 Hrs
Total Marks : 20
    Answer all the questions
    20 x 1 = 20
  1. The signal is aff ected by noise in a communication system

    (a)

    At the transmitter

    (b)

    At the modulator

    (c)

    In the channel

    (d)

    At the receiver

  2. The internationally accepted frequency deviation for the purpose of FM broadcasts

    (a)

    75 kHz

    (b)

    68 kHz

    (c)

    80 kHz

    (d)

    70 kHz

  3. The loss of strengh of a signal while propagating through a medium is known as_________.

    (a)

    modulation

    (b)

    absorption

    (c)

    transmission

    (d)

    Attenuation

  4. Modulation is the process of superposing

    (a)

    low frequency audio signal on high frequency radio waves

    (b)

    low frequency radio signal on low frequency audio waves

    (c)

    high frequency radio signal on low frequency audio

    (d)

    high frequency audio signal on low frequency radio waves

  5. Large band width for higher data is achieved by using

    (a)

    Large band width for higher data is achieved
    by using

    (b)

    high frequency audio wave

    (c)

    low frequency carrier wave

    (d)

    low frequency audio wave

  6. Which of the following is an example of breadcast made of communication?

    (a)

    Radio

    (b)

    Television

    (c)

    Mobile

    (d)

    both (a) & (b)

  7. The made of propagation used by short wave broadcast services is

    (a)

    space wave

    (b)

    skywave

    (c)

    ground wave

    (d)

    both (a) & (c)

  8. FM broadcost is preferred over AM broadcast because

    (a)

    It is less noisy

    (b)

    reproduction is of much better quality

    (c)

    it is more noisy

    (d)

    both (a) & (b)

  9. A gound receiver in line of sight communication cannot receive direct waves due to

    (a)

    its low frequency

    (b)

    curvature of each

    (c)

    its high intensity

    (d)

    smaller antenna

  10. In frequency modulation

    (a)

    the amplitude of modulated wave varies as frequency

    (b)

    the frequency of modulated wave varies as amplitute the frequency

    (c)

    the amplitude of modulated wave varies as amplitute of carrier wave

    (d)

    the frequency of modulated wave varies as frequency of modulating wave

  11. In modulation process) radio frequency wave is termed as

    (a)

    modulated wave

    (b)

    modulating wave

    (c)

    carrier wave

    (d)

    none

  12. An EM wave travels in free space, only one of the following can happen to them

    (a)

    reflection

    (b)

    absorption

    (c)

    refraction

    (d)

    attenuation

  13. The most commonly,employed modulation in satellite communication is the

    (a)

    amplititude modulation

    (b)

    FM

    (c)

    phase modulation

    (d)

    all

  14. The radio waves can be sent from one place to another through _________ propagation.

    (a)

    ground wave

    (b)

    sky wave

    (c)

    space wave

    (d)

    all of above

  15. When the transmitting and receiving antennas are close to the ground, the type 'of radio-wave propagation is_________ propagation.

    (a)

    ground

    (b)

    space

    (c)

    sky

    (d)

    ionospheric

  16. Long distance radio communication employs _______ wave propagation.

    (a)

    ground

    (b)

    sky

    (c)

    space

    (d)

    surface

  17. Skip distance the shortest distance between

    (a)

    the point of transmission and the point of reception

    (b)

    the uplink and the downlink station

    (c)

    the transmitter and the target

    (d)

    the receiver and the target

  18. After the angle of refraction becomes 90o at the ionosphere, the wave travels _________.

    (a)

    faster

    (b)

    through space

    (c)

    in a straight line

    (d)

    towards the earth

  19. The component of the modulated wave, which has a greater frequency than that of the carrier is called __________.

    (a)

    upper side band

    (b)

    middle side band

    (c)

    lower side band

    (d)

    stoke's band

  20. The intermediate frequency is the _________ oscillator frequency and radio frequency.

    (a)

    product

    (b)

    sum of

    (c)

    difference between

    (d)

    integral of

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