JEE Questions for Physics Communication System Quiz 1 - MCQExams.com

In ruby laser, the stimulated emission is due to transition from
  • metastable state to any lower state
  • any higher state to lower state
  • metastable state to ground state
  • any higher state to ground state
The hottest planet of solar system is
  • Mars
  • Mercury
  • Venus
  • Pluto
The distance of Venus from the sun is 0.72 AU. The orbital period of the Venus is
  • 200 days
  • 320 days
  • 225 days
  • 325 days
If a radio receiver amplifies all the signal frequencies equally well, it is said to have high
  • fidelity
  • distortion
  • sensibility
  • sensitivity
  • selectivity
The waves used for Line of Sight (LOS) communication are
  • ground waves
  • space waves
  • sound waves
  • sky waves
Choose the electromagnetic radiation relevant to telecommunication
  • ultraviolet
  • infrared
  • visible
  • microwave
A laser beam is used for carrying out surgery because it
  • is highly monochromatic
  • is highly coherent
  • is highly directional
  • can be sharply focused
Which of the following is not the main characteristic of laser beam?
  • High irradiance
  • High divergence
  • Highly monochromatic
  • Highly coherent
The principle of laser action involves
  • amplification of particular frequency emitted by the system
  • population inversion
  • stimulated emission
  • All of the above
In a video signal for transmission of picture, what value of bandwidth is used in communication system?
  • 2.4 MHz
  • 4.2 MHz
  • 24 MHz
  • 42 MHz
If Ec= 20 sin 105 πt and Em= 10 sin 400 πt are carrier and modulating signals respectively, the modulation index is
  • 56%
  • 30%
  • 50%
  • 48%
  • 60%
The antenna current of an AM transmitter is 8 A when only the carrier is sent, but it increases to 8.93A when the carrier is modulated by single sine wave. Find the percentage modulation.
  • 60.1%
  • 70.1%
  • 80.1%
  • 50.1%
In frequency modulated wave,
  • frequency varies with time
  • amplitude varies with time
  • both frequency and amplitude vary with time
  • both frequency and amplitude are constant
The distance of coverage of a transmitting antenna is 12.8 km. Then, the height of the antenna is
(given that radius of the earth = 6400 km)
  • 6.4 m
  • 12.8 m
  • 3.2 m
  • 16 m
  • 25.6 m
What should be minimum length of antenna for efficient transmission of signals of wavelength λ ?
  • λ/2
  • λ/3
  • λ/4
  • λ/5
What fraction of the surface area of the earth can be covered to establish communication by one geostationary satellite?
  • 1/2
  • 1/3
  • 1/4
  • 1/8
If sky wave with a frequency of 50 MHz is incident on D region at an angle of 30°, then angle of refraction is
  • 15°
  • 30°
  • 60°
  • 45°
The characteristic impedance of a coaxial cable is of the order of
  • 50 Ω
  • 200 Ω
  • 270 Ω
  • None of these
Which one of the following is a full duplex transmission system?
  • TV
  • Radio
  • Telephone
  • Walky-talky (wireless used in the army)
The characteristic impedance (Z0 ) of free space is
  • 377 Ω
  • 357 Ω
  • 100 Ω
  • 1000 Ω
What is the minimum length of antenna required to transmit a radio signal of frequency 20 MHz ?
  • 5.0 m
  • 7.5 m
  • 2.0 m
  • 3.75 m
What happens inside optical fibre?
  • Diffraction
  • Polarisation
  • Interference
  • Total internal reflection
An antenna is of height 500 m. What will be its range (Radius of the earth is 6400 km)?
  • 800 km
  • 100 km
  • 50 km
  • 80 km
Antenna is
  • inductive
  • capacitive
  • resistive above its resonant frequency
  • resistive at resonant frequency
How many photons are emitted by a laser source of 5 × 10-3 W operating at 632.2 nm in 2s ?
  • 3.2 × 1016
  • 1.6 × 1016
  • 4 × 1016
  • None of these
Ozone layer blocks the radiations of wavelength
  • less than 3 × 10-7 m
  • equal to 3 × 10-7 m
  • more than 3 × 10-7 m
  • All of the above
Fainted stars are called
  • dwarfs
  • sixth magnitude stars
  • second magnitude
  • zero magnitude stars
Flash spectrum confirms a/an
  • magnetic storm
  • earthquake
  • lunar eclipse
  • total solar eclipse
The galaxy in which we live is
  • Milkyway
  • Radio galaxy
  • Spiral galaxy
  • None of these
The rest mass of a body is m0 , if it moves with a velocity of 0.6 c, then its relativistic mass is m, then
  • m < m0
  • m = m0
  • m > m0
  • None of these
0:0:1


Answered Not Answered Not Visited Correct : 0 Incorrect : 0

Practice Physics Quiz Questions and Answers