Class 12 Communication Systems CBSE Questions & Answers

Class 12 · Communication Systems

This is Physics Class 12 Communication Systems CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
for a signal to be reproduced without distortion
  • A
    only the fundamental and first harmonic is required
  • B
    none of these
  • C
    only the fundamental is required
  • D
    All the harmonics should be present
    Correct
2
Audio signals have a maximum bandwidth of about
  • A
    2 kHz
  • B
    200 kHz
  • C
    2000 kHz
  • D
    20 kHz
    Correct
3
Coaxial cables have a bandwidth in the range of
  • A
    750 GHz
  • B
    750 Hz
  • C
    750 kHz
  • D
    750 MHz
    Correct
4
Transmission bandwidth of fiber optic communication can be up to
  • A
    100 GHz
    Correct
  • B
    416 MHz
  • C
    100 Hz
  • D
    110 kHz
5
To radiate signals with high efficiency, the antennas should have a size
  • A
    none of these
  • B
    much greater than the wavelength \(\lambda \) of the signal
  • C
    comparable to the wavelength \(\lambda \) of the signal (at least \({\rm{ }}\lambda {\rm{4}}\))
    Correct
  • D
    much smaller than the wavelength \(\lambda \) of the signal
6
In ground wave propagation the earth
  • A
    attenuates the radiated signal as a result of energy absorption by it
    Correct
  • B
    none of these
  • C
    amplifies the radiated signal
  • D
    reflects the waves
7
Ground wave propagation is used for
  • A
    Low frequency greater than 500 MHz and less than 1GHz
  • B
    VLF few MHz
    Correct
  • C
    High frequency greater than 10GHz
  • D
    High frequency greater than 1GHz
8
In sky wave propagation the ionosphere
  • A
    none of these
  • B
    absorbs the radiated signal
  • C
    reflects the radiated signal
    Correct
  • D
    transmits the radiated signal
9
Sky wave propagation is possible in the range from
  • A
    few MHz up to 30 to 40 MHz
    Correct
  • B
    few Hz up to 30 to 40 kHz
  • C
    none of these
  • D
    few kHz up to 3.0 to 4.0 MHz
10
Space wave propagation can be
  • A
    none of these
  • B
    Line of sight communication or satellite communication
    Correct
  • C
    can only be transmitted from a space station
  • D
    can only be transmitted from a polar satellite
11
To increase the range of line of sight communication
  • A
    decrease the height of receiving tower only
  • B
    decrease the height of transmitting tower only
  • C
    decrease the height of both transmitting and receiving towers
  • D
    increase the height of both transmitting and receiving towers
    Correct
12
With reference to the figure the value of \({{\rm{d}}_{\rm{M}}}\) can be calculated by
Question 12 figure 1
  • A
    \({d_M} = \sqrt {2R{h_T}} + \sqrt {R{h_R}} \)
  • B
    \({d_M} = \sqrt {2R{h_T}} + \sqrt {2R{h_R}} \)
    Correct
  • C
    \({d_M} = \sqrt {2R{h_R}} \)
  • D
    \({d_M} = \sqrt {2R{h_T}} \)
13
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 LOS mode? Given radius of earth is 6.4 \( \times {\rm{ 1}}{0^{\rm{6}}}\) m.
  • A
    58.5 km
  • B
    55.5 km
  • C
    45.5 km
    Correct
  • D
    48.5 km
14
baseband signal refers to the
  • A
    signal containing the message or information during modulation
  • B
    signal containing the message or information just after receiving
  • C
    signal containing the message or information before modulation
    Correct
  • D
    signal containing the message or information after modulation
15
need for modulation arises from antenna considerations. If base band signal is to be transmitted then
  • A
    shape of antenna would be complex
  • B
    size of antenna would be very small
  • C
    none of these
  • D
    size of antenna would be huge
    Correct