MCQs
Communication Systems(12th Grade -Physics)
Total Questions : 167
| Page 1 of 17 pages
Answer: Option C. -> 45.5 km
:
C
√2×64×105×32+√2×64×105×50 = 64 × 10^2 × √10 + 8 × 10^3 × √10m = 144 × 10^2 × √10= 45.5 km
:
C
√2×64×105×32+√2×64×105×50 = 64 × 10^2 × √10 + 8 × 10^3 × √10m = 144 × 10^2 × √10= 45.5 km
Answer: Option B. -> >1
:
B
When m > 1 then carrier is said to be over modulated.
:
B
When m > 1 then carrier is said to be over modulated.
Answer: Option A. -> h12
:
A
d = √2hR⇒dαh12
:
A
d = √2hR⇒dαh12
Answer: Option D. -> They have high degree of parallelism
:
D
Laser beams are perfectly parallel, so that they are very narrow and can travel a long distance without spreading. This is the feature of laser while monochromatic and coherent are characteristics only.
:
D
Laser beams are perfectly parallel, so that they are very narrow and can travel a long distance without spreading. This is the feature of laser while monochromatic and coherent are characteristics only.
Answer: Option B. -> Optical fibres are subject to electromagnetic interference from outside.
:
B
Optical fibres are not subjected to electromagnetic interference from outside.
:
B
Optical fibres are not subjected to electromagnetic interference from outside.
Answer: Option A. -> 1490, 1510
:
A
Here, fc = 1.5 MHz = 1500 kHz ,fm = = 10 kHz
∴ Low side band frequency
= fc - fm = 1500 kHz - 10 kHz = 1490 kHz
Upper side band frequency
= fc + fm = 1500 kHz + 10 kHz = 1510 kHz
:
A
Here, fc = 1.5 MHz = 1500 kHz ,fm = = 10 kHz
∴ Low side band frequency
= fc - fm = 1500 kHz - 10 kHz = 1490 kHz
Upper side band frequency
= fc + fm = 1500 kHz + 10 kHz = 1510 kHz
Question 7. Read the assertion and reason carefully to mark the correct option out of the options given below:
Assertion : The electrical conductivity of earth's atmosphere decreases with altitude.
Reason : The high energy particles (i.e. g-rays and cosmic rays) coming from outer space and entering our earth's atmosphere cause ionisation of the atoms of the gases present there and the pressure of gases decreases with increase in altitude.
(a)If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b)If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c)If assertion is true but reason is false.
(d)If the assertion and reason both are false.
(e)If assertion is false but reason is true.
Assertion : The electrical conductivity of earth's atmosphere decreases with altitude.
Reason : The high energy particles (i.e. g-rays and cosmic rays) coming from outer space and entering our earth's atmosphere cause ionisation of the atoms of the gases present there and the pressure of gases decreases with increase in altitude.
(a)If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b)If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c)If assertion is true but reason is false.
(d)If the assertion and reason both are false.
(e)If assertion is false but reason is true.
Answer: Option E. -> e
:
E
The electrical conductivity of earth's atmosphere increases with height so assertion is false.
When high energy particles enters in earth's atmosphere. They ionises the gases present in atmosphere. Also as we go up, the air thins out gradually and air pressure decreases.
:
E
The electrical conductivity of earth's atmosphere increases with height so assertion is false.
When high energy particles enters in earth's atmosphere. They ionises the gases present in atmosphere. Also as we go up, the air thins out gradually and air pressure decreases.
Answer: Option D. -> Both (a) and (b)
:
D
A very small part of light energy is lost from an optical fiber due to absorption or due to light leaving the fiber as a result of scattering of light sideways by impurities in the glass fiber.
:
D
A very small part of light energy is lost from an optical fiber due to absorption or due to light leaving the fiber as a result of scattering of light sideways by impurities in the glass fiber.
Answer: Option B. -> 1703 nm
:
B
Limiting value of hv is Eg, such that hv = hcλ = Eg
or λ=hcEg=6.63×10−34J−s×3×108ms−10.73×1.6×10−19J
= 1703 nm
:
B
Limiting value of hv is Eg, such that hv = hcλ = Eg
or λ=hcEg=6.63×10−34J−s×3×108ms−10.73×1.6×10−19J
= 1703 nm
Answer: Option B. -> The frequency of modulated wave varies as amplitude of modulating wave
:
B
The process of changing the frequency of a carrier wave (modulated wave) in accordance with the audio frequency signal (modulating wave) is known as frequency modulation (FM).
:
B
The process of changing the frequency of a carrier wave (modulated wave) in accordance with the audio frequency signal (modulating wave) is known as frequency modulation (FM).