Out of the following electromagnetic radiations, which has the sh

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 Multiple Choice QuestionsMultiple Choice Questions

21.

Which one of the following statements is wrong ?

  • Radio waves in the frequency range 30 MHz to 60 MHz are called sky waves.

  • Radio horizon of the transmitting antenna for space wave is dT = 2RhT (R = radius of earth, hT = height of transmitting antenna)

  • Within the skip distance neither the ground waves nor the sky waves are received

  • The principle of fibre optical communication is total internal reflection


22.

A plane electromagnetic wave travels in free space along x-axis. At a particular point in space, the electric field along y-axis is 9.3 Vm-1. The magnetic induction is

  • 3.1 × 10-8 T

  • 3 × 10-5 T

  • 3 × 10-6 T

  • 9.3 × 10-6 T


23.

The dielectric constant of air is 1.006. The speed of electromagnetic wave travelling in air is a x 108 ms-1, where a is about

  • 3

  • 3.88

  • 2.5

  • 3.2


24.
  1. The wavelength of microwaves is greater than that of UV-rays.
  2. The wavelength of IR rays is lesser than that of UV-rays.
  3. The wavelength of microwaves is lesser than that of IR rays.
  4. Gamma rays have shortest wavelength in the electromagnetic spectrum.
  5. Of the above statements

  • A and B are true

  • B and C are true

  • A and D are true

  • A and C are true


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25.

The frequency of X-rays, γ-rays and ultraviolet rays are respectively a, b and c then

  • a < b, b > c

  • a > b, b > c

  • a > b, b < c

  • a < b, b < c


26.

The waves relevant to telecommunications are

  • visibe light

  • infrared

  • ultraviolet

  • microwave


27.

Velocity of electromagnetic waves in a medium depends upon

  • thermal properties of medium

  • mechanical and electrical properties of medium

  • electrical and magnetic properties of the medium

  • mechanical and magnetic properties of the medium


28.

In the electromagnetic spectrum, the visible spectrum lies between

  • radiowaves and microwaves

  • infrared and ultraviolet rays

  • microwaves and infrared spectrum

  • X-ray and γ-ray spectrum


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29.

Maxwell in his famous equation of electromagnetism introduced the concept

  • AC current

  • DC current

  • displacement current

  • impedance


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30.

Out of the following electromagnetic radiations, which has the shortest wavelength ?

  • Radiowaves

  • Infrared

  • X-rays

  • Visible light


C.

X-rays

X-rays have shortest wavelength out of the given radiations.


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