Class 12 Physics Chapter 8 Electromagnetic Waves Solved Question Answers

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Questions
1 Who first demonstrated the existence of em waves?
A Hertz
B Maxwell
C Ampere
D Faraday

Answer:Hertz
2 Electromagnetic waves have a speed of
A 3 × 105 kms-1
B 3 × 106 kms-1
C 3 × 107 kms-1
D 3 × 108 kms-1

Answer:3 × 105 kms-1
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3 Name the law which states that a varying electric field produces a magnetic field:
A Biot-Savart’s law
B Faraday’s law
C Modified Ampere’s law
D None of these

Answer:Modified Ampere’s law
4 The dimensions of Class 12 Physics Chapter 8 Electromagnetic Waves
A potential
B charge
C current
D None of these

Answer:potential
5 The dimensional formula of is:
A [MLT-2A-1]
B [ML0T-2A-1]
C [ML0T-3A-1]
D None of these

Answer:[ML0T-2A-1]
6 Maxwell’s equation involving Class 12 Physics Chapter 8 Electromagnetic Waves is obtained-from:
A Ampere’s law
B Gauss’s law
C Faraday’s law
D Biot-Savart’s law

Answer:Faraday’s law
7 An EMW of v = 3 MHz passes from vacuum into dielectric medium with permittivity Er = 4, then:
A Wavelength is doubled and the frequency remains unchanged
B Wavelength is doubled and the frequency become half
C Wavelength is halved and the frequency remains unchanged
D Wavelength and frequency both remain unchanged

Answer:Wavelength is halved and the frequency remains unchanged
8 Solar radiation is :
A transverse EMW
B longitudinal EMW
C both (a) and (b)
D None of these

Answer:transverse EMW
9 Light Year is the unit of:
A distance
B time
C energy
D intensity of light

Answer:distance
10 Frequency of a wave is 6 × 1015. Hz. The wave is :
A Radiowave
B Microwave
C X-ray
D Ultra violet

Answer:Ultra violet
11 If Class 12 Physics Chapter 8 Electromagnetic Waves is the magnetic field vector and Class 12 Physics Chapter 8 Electromagnetic Waves is the electric field vector in an em wave, then which of the following relations is correct? Here c is the speed of fight:
A c = E/B
B c = B/E
C c = B/E
D c = 1/EB

Answer:c = E/B
12 Which of the following has the dimensions of current?
A Class 12 Physics Chapter 8 Electromagnetic Waves
B Class 12 Physics Chapter 8 Electromagnetic Waves
C Class 12 Physics Chapter 8 Electromagnetic Waves
D Class 12 Physics Chapter 8 Electromagnetic Waves

Answer:C
13 The ratio of the amplitude of the magnetic field to the amplitude of the electric field for electromagnetic wave propagation in a vacuum is equal to
A Unity
B Speed of light in vacuum
C Reciprocal of the speed of light in vacuum
D The ratio of magnetic permeability to electrical susceptibility in a vacuum.

Answer:Reciprocal of the speed of light in vacuum
14 To which part of the spectrum does EM waves belong if the energy of the wave is of the order of 15 KeV.
A X rays
B Infrared rays
C Ultraviolet rays
D Gamma rays

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

Answer:Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of the wave.
16 In an electromagnetic wave in free space, the root mean square value of the electric field is 6 V/m. The peak value of the magnetic field is
A 2.83 x 10-8 T
B 1.51 x 10-8 T
C 0.80 x 10-8 T
D 4 x 10-8 T

Answer:2.83 x 10-8 T
17 In electromagnetic waves the phase difference between electric field vector and magnetic field vector is
A zero
B π/2
C π
D π/3

Answer:zero
18 Which of the following can be used to produce a propagating electromagnetic wave?
A Charge moving at a constant speed
B Chargeless particle
C Stationary charge
D An accelerating charge

Answer:An accelerating charge
19 Which of the following rays are not electromagnetic waves?
A Gamma rays
B Beta rays
C Heat rays
D X rays

Answer:Beta rays
20 The direction in which electromagnetic waves propagate is the same as that of
A Class 12 Physics Chapter 8 Electromagnetic Waves
B Class 12 Physics Chapter 8 Electromagnetic Waves
C
D

Answer:A

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