Class 12 Electromagnetic Waves CBSE Questions & Answers

Class 12 · Electromagnetic Waves

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

Questions & Answers

1
According to Maxwell’s equations
  • A
    time-varying magnetic field acts as a source of electric field and time-varying electric field acts as a source of magnetic field
    Correct
  • B
    time-varying magnetic field acts as a sink of electric field
  • C
    time-varying magnetic field produce as a static electric field
  • D
    time-varying magnetic field vanishes in electric field
2
Maxwell’s displacement current is a response to
  • A
    inconsistency in the Faraday’s law
  • B
    inconsistency in the Ampere’s law
    Correct
  • C
    inconsistency in the gauss’s law
  • D
    inconsistency in the Lenz’s law
3
Without the concept of displacement current it is not possible to correctly apply Ampere’s law on a path parallel to the plates of parallel plate capacitor C in
  • A
    the region between source and the plates
  • B
    the region leading to plate 2
  • C
    the region leading to plate 1
  • D
    the region between the plates
    Correct
4
Displacement current is given by
  • A
    \({\varepsilon _0}\) \({{d2{\emptyset _E}} \over {dt2}}\)
  • B
    \({{d{\emptyset _E}} \over {dt}}\)
  • C
    \({\varepsilon _0}\) \({{{d_E}} \over {dt}}\)
  • D
    \({\varepsilon _0}\) \({{d{\emptyset _E}} \over {dt}}\)
    Correct
5
Which of these mechanisms can be used to produce electromagnetic waves?
  • A
    point charge oscillating in simple harmonic motion
    Correct
  • B
    point charge drifting slowly
  • C
    point charge travelling in a circle at constant velocity
  • D
    point charge travelling in a straight line with constant velocity
6
The electric field of a plane electromagnetic wave travelling in +ve z direction is described by
  • A
    \({{\rm{E}}_{\rm{x}}} = {\rm{ }}{{\rm{E}}_0}{\rm{sin }}\left( {{\rm{2kz}}} \right)\)
  • B
    \({{\rm{E}}_{\rm{x}}} = {\rm{ }}{{\rm{E}}_0}{\rm{sin }}\left( {{\rm{kz}}} \right)\)
  • C
    \({{\rm{E}}_{\rm{x}}} = {\rm{ }}{{\rm{E}}_0}{\rm{sin }}\left( {{\rm{kz}}-\omega {\rm{t}}} \right)\)
    Correct
  • D
    \({{\rm{E}}_{\rm{x}}} = {\rm{ }}{{\rm{E}}_0}{\rm{sin }}\left( {{\rm{kz}} + \omega {\rm{t }}} \right)\)
7
The magnetic field of a plane electromagnetic wave travelling in +ve z direction is described by
  • A
    \({{\rm{B}}_{\rm{y}}} = {\rm{ }}{{\rm{B}}_0}{\rm{sin }}\left( {{\rm{ kz}}} \right)\)
  • B
    \({{\rm{B}}_{\rm{y}}} = {\rm{ }}{{\rm{B}}_0}{\rm{sin }}\left( {{\rm{2kz}}} \right)\)
  • C
    \({{\rm{B}}_{\rm{y}}} = {\rm{ }}{{\rm{B}}_0}{\rm{sin }}\left( {{\rm{ kz }}-{\rm{ }}\omega {\rm{t }}} \right)\)
    Correct
  • D
    \({{\rm{B}}_{\rm{y}}} = {\rm{ }}{{\rm{B}}_0}{\rm{sin }}\left( {{\rm{ kz }} + {\rm{ }}\omega {\rm{t }}} \right)\)
8
The direction of propagation of an electromagnetic plane wave is
  • A
    perpendicular to magnetic field vector
  • B
    parallel to both electric field vector and the magnetic field vector
  • C
    perpendicular to both electric field vector and the magnetic field vector
    Correct
  • D
    perpendicular to electric field vector
9
Angular frequency \(\omega \) and wave vector k are related by
  • A
    k = \({{2\pi } \over \lambda }\)
    Correct
  • B
    k = \({\pi \over {2\lambda }}\)
  • C
    k = \({{4\pi } \over \lambda }\)Hz
  • D
    k = \({\pi \over \lambda }\)
10
Plane electromagnetic waves are
  • A
    Standing waves
  • B
    Shock waves
  • C
    transverse waves
  • D
    longitudinal waves
    Correct
11
In plane electromagnetic wave propagation velocity V, wavelength \(\lambda \) and frequency \(\vartheta \) are related by
  • A
    V = \({\rm{2}}\vartheta \lambda \)
  • B
    V = \(\vartheta \lambda /\pi \)
  • C
    V = \(\vartheta \lambda \)
    Correct
  • D
    V = \(\vartheta \lambda \pi \)
12
Velocity of plane electromagnetic waves in vacuum equals
  • A
    speed of subsonic rockets
  • B
    speed of sonic boom
  • C
    speed of sound
  • D
    speed of light
    Correct
13
Magnitude of the electric and the magnetic fields in an plane electromagnetic wave are related by
  • A
    \({{\rm{B}}_0}\) = \({{\pi {E_0}} \over c}\)
  • B
    \({{\rm{B}}_0}\) = \({{{E_0}} \over c}\)
    Correct
  • C
    \({{\rm{B}}_0}\)= \(2{{{E_0}} \over c}\)
  • D
    \({{\rm{B}}_0}\)= \({{{E_0}} \over {c\pi }}\)
14
The speed of plane electromagnetic waves is maximum in
  • A
    glass
  • B
    vacuum
    Correct
  • C
    tourmaline
  • D
    water
15
Radio waves for FM radio have a frequency about
  • A
    100 KHz
  • B
    100 MHz
    Correct
  • C
    100 GHz
  • D
    100 Hz