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
Applying Kirchhoff’s first rule (junction rule) valid at each plate of the capacitor
Question 1 figure 1
  • A
    conduction current \( \ne \) displacement current
  • B
    conduction current = displacement current
    Correct
  • C
    conduction current \( < \) displacement current
  • D
    conduction current \( > \) displacement current
2
A parallel plate capacitor made of circular plates each of radius R = 6.0 cm has a capacitance C = 100 pF. The capacitor is connected to a 230 V ac supply with a (angular) frequency of 300 rad \({{\rm{s}}^{-{\rm{1}}}}\). rms value of the conduction current is
  • A
    7.1 \(\mu {\rm{A}}\)
  • B
    7.9 \(\mu {\rm{A}}\)
  • C
    7.3 \(\mu {\rm{A}}\)
  • D
    6.9 \(\mu {\rm{A}}\)
    Correct
3
What physical quantity is the same for X-rays of wavelength \({\rm{1}}{0^{-{\rm{1}}0}}\) m, red light of wavelength 6800 \(\mathop A\limits^0 \) and radio waves of wavelength 500m?
  • A
    frequency
  • B
    speed
    Correct
  • C
    phase
  • D
    energy
4
Plane electromagnetic wave travels in vacuum along z-direction. If the frequency of the wave is 30 MHz, its wavelength is
  • A
    12 m
  • B
    13 m
  • C
    10 m
    Correct
  • D
    11 m
5
7.5 MHz to 12 MHz band corresponds to wavelength band of
  • A
    40 m – 25 m
    Correct
  • B
    40 m – 25 m
  • C
    40 m – 25 m
  • D
    40 m – 25 m
6
A charged particle oscillates about its mean equilibrium position with a frequency of \({\rm{1}}{0^{\rm{9}}}\) Hz. Frequency of the electromagnetic waves produced by the oscillator is
  • A
    \({\rm{1}}{0^{\rm{9}}}\)
    Correct
  • B
    400 MHz
  • C
    200 MHz
  • D
    600 MHz
7
The amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum is \({{\rm{B}}_0}\)= 510 nT. Amplitude of the electric field part of the wave is
  • A
    153 N/C
    Correct
  • B
    163N/C
  • C
    158N/C
  • D
    173N/C
8
Suppose that the electric field amplitude of an electromagnetic wave is \({{\rm{E}}_0}\) = 120 N/C and that its frequency is ν = 50.0 MHz \({{\rm{B}}_0}\), \(\omega \), k, and \(\lambda \). are
  • A
    450 nT, 3.0 \( \times \) 108 rad/s, 1.05 rad/m, 6.00 m
  • B
    500 nT, 3.3 \( \times \) 108 rad/s, 1.05 rad/m, 6.00 m
  • C
    550 nT, 3.14 \( \times \) 108 rad/s, 1.05 rad/m, 6.00 m
  • D
    400 nT, 3.14 \( \times \) 108 rad/s, 1.05 rad/m, 6.00 m
    Correct
9
Use the formula E = hν (for energy of a quantum of radiation: photon) and obtain the photon energy in units of eV for for {tex}\lambda {tex} = 1 m
  • A
    1.44 \( \times {\rm{ 1}}{0^{ - {\rm{6}}}}{\rm{eV}}\)
  • B
    1.24 \( \times {\rm{ 1}}{0^{ - {\rm{6}}}}{\rm{eV}}\)
    Correct
  • C
    1.34 \( \times {\rm{ 1}}{0^{ - {\rm{6}}}}{\rm{eV}}\)
  • D
    1.54 \( \times {\rm{ 1}}{0^{ - {\rm{6}}}}{\rm{eV}}\)
10
In a plane electromagnetic wave, the electric field oscillates sinusoidally at a frequency of \({\rm{2}}.0{\rm{ }} \times {\rm{ 1}}{0^{{\rm{1}}0}}\) Hz and amplitude 48 V \({{\rm{m}}^{-{\rm{1}}}}\).wavelength of the wave and amplitude of the oscillating magnetic field are
  • A
    1.8 \( \times {\rm{ 1}}{0^{-{\rm{2}}}}{\rm{m}}\), 1.8 \( \times {\rm{ 1}}{0^{-{\rm{7}}}}\)T
  • B
    2.5 \( \times {\rm{ 1}}{0^{-{\rm{2}}}}{\rm{m}}\), 2.6 \( \times {\rm{ 1}}{0^{-{\rm{7}}}}\) T
  • C
    2.2 \( \times {\rm{ 1}}{0^{-{\rm{2}}}}{\rm{m}}\), 1.6 \( \times {\rm{ 1}}{0^{-{\rm{7}}}}\) T
  • D
    1.5\( \times {\rm{ 1}}{0^{-{\rm{2}}}}{\rm{m}}\), 1.6 \( \times {\rm{ 1}}{0^{-{\rm{7}}}}\)T
    Correct
11
Suppose that the electric field part of an electromagnetic wave in vacuum is E = {(3.1 N/C) cos [(1.8 rad/m) y + (5.4 \( \times {\rm{ 1}}{0^{\rm{6}}}\) rad/s)t]} i . Wavelength \(\lambda \), frequency ν and the amplitude of the magnetic field part of the wave are
  • A
    3.5 m, 86 MHz, 100 nT
    Correct
  • B
    3.5 m, 90 MHz, 200 nT
  • C
    5.5 m, 96 MHz, 100 nT
  • D
    4.0 m, 86 MHz, 250 nT
12
About 5\(\% \) of the power of a 100 W light bulb is converted to visible radiation. What is the average intensity of visible radiation at a distance of 1m from the bulb and at a distance of 10 m are
  • A
    0.45 \({\rm{W}}/{{\rm{m}}^{\rm{2}}}\), 0.004 \({\rm{W}}/{{\rm{m}}^{\rm{2}}}\)
  • B
    0.5 \({\rm{W}}/{{\rm{m}}^{\rm{2}}}\), 0.004 \({\rm{W}}/{{\rm{m}}^{\rm{2}}}\)
  • C
    0.4 \({\rm{W}}/{{\rm{m}}^{\rm{2}}}\), 0.004 \({\rm{W}}/{{\rm{m}}^{\rm{2}}}\)
    Correct
  • D
    0.55 \({\rm{W}}/{{\rm{m}}^{\rm{2}}}\), 0.004 \({\rm{W}}/{{\rm{m}}^{\rm{2}}}\)
13
Use the formula \({\lambda _{\rm{m}}}\) T = 0.29 cmK to obtain the characteristic temperature range for \({\lambda _{\rm{m}}} = {\rm{ 1}}{0^{ - {\rm{6}}}}\)m
  • A
    3000 K
  • B
    2900 K
    Correct
  • C
    3100 K
  • D
    3200 K
14
Use the formula \({\lambda _{\rm{m}}}\) T = 0.29 cmK to obtain the characteristic temperature range for \({\lambda _{\rm{m}}} = {\rm{ 5 }} \times {\rm{ 1}}{0^{-{\rm{7}}}}\)m
  • A
    7000 K
  • B
    7500 K
  • C
    6500 K
  • D
    6000 K
    Correct
15
State the part of the electromagnetic spectrum to which 21 cm (wavelength emitted by atomic hydrogen in interstellar space).belongs
  • A
    Visible
  • B
    Microwave
  • C
    Ultraviolet
  • D
    Radio (short wavelength end)
    Correct