MCQ On Class 12 Physics Chapter 8 Electromagnetic Waves

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Questions
1 The waves used by artificial satellites for communication is
A microwaves
B infrared waves
C radio waves
D X-rays

Answer:microwaves
2 A charged particle oscillates about its mean equilibrium position with a frequency of 109 Hz. The frequency of electromagnetic waves produced by the oscillator is
A 106 Hz
B 107 Hz
C 108 Hz
D 109 Hz

Answer:109 Hz
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3 Which of the following has/have zero average value in a plane electromagnetic wave?
A Both magnetic and electric fields
B Electric field only
C Magnetic field only
D None of these

Answer:Both magnetic and electric fields
4 Which of the following statement is false for the properties of electromagnetic waves?
A Both electric and magnetic field vectors attain the maxima and minima at the same place and same time.
B The energy in electromagnetic waves is divided equally between electric and magnetic field vectors
C Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of wave.
D These waves do not require any material medium for propagation.

Answer:Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of wave.
5 If a variable frequency ac source is connected to a capacitor then with decrease in frequency the displacement current will
A increase
B decrease
C remains constant
D first decrease then increase

Answer:decrease
6 Maxwell in his famous equations of electromagnetism introduced the concept of
A ac current
B displacement current
C impedance
D reactance

Answer:displacement current
7 The ultra high frequency band of radio waves in electromagnetic wave is used as in
A television waves
B cellular phone communication
C commercial FM radio
D both (a) and (c)

Answer:cellular phone communication
8 An electromagnetic wave can be produced, when charge is
A moving with a constant velocity
B moving in a circular orbit
C falling in an electric field
D both (b) and (c)

Answer:both (b) and (c)
9 Which of the following electromagnetic waves is used in medicine to destroy cancer cells?
A IR-rays
B Visible rays
C Gamma rays
D Ultraviolet rays

Answer:Gamma rays
10 The conduction current is same as displacement current when source is
A ac only
B dc only
C either ac or dc
D neither dc nor ac

Answer:either ac or dc
11 Ampere’s circuital law was modified by:
A Laplace
B Gauss
C Maxwell
D Hertz

Answer:Maxwell
12 Choose the wrong statement?
A Electromagnetic waves are transverse
B Electromagnetic waves travel with the speed of light in free space
C Electromagnetic waves are produced by accelerating charges
D Electromagnetic waves travel with the same speed in all media

Answer:Electromagnetic waves travel with the same speed in all media
13 The existence of EMW was experimentally established by :
A Sir S. C. Bose
B Maxwell
C Marconi
D Hertz

Answer:Sir S. C. Bose
14 The dimensions of E/Bare same as that of:
A charge
B current
C velocity
D acceleration

Answer:velocity
15 EMW are produced by:
A charge in uniform motion only
B charge at rest only
C accelerated or decelerated charge only
D all of the above

Answer:accelerated or decelerated charge only
16 Displacement current is due to:
A the flow of electrons
B the Varying electric field
C the ionization of atmosphere
D the flow of protons

Answer:the Varying electric field
17 Choose the wave relevant to telecommunication :
A ultraviolet
B infrared
C microwave
D visible light

Answer:microwave
18 Displacement current is always :
A equal to conduction current
B less than conduction current
C greater than conduction current
D the sum of current due to flow of positive and negative ions

Answer:equal to conduction current
19 Which of the following EMW has highest wavelength?
A X-ray
B ultraviolet rays
C infrared rays
D microwaves

Answer:infrared rays
20 Which of the following laws was modified by Maxwell by introducing the displacement current?
A Gauss’s law
B Ampere’s law
C Biot-Savart’s law
D None of theseL

Answer:Ampere’s law

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