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Electromagnetic Waves Class 12 MCQs Questions with Answers
Solving the Electromagnetic Waves Multiple Choice Questions of Class 12 Physics Chapter 8 MCQ can be of extreme help as you will be aware of all the concepts. These MCQ Questions on Electromagnetic Waves Class 12 with answers pave for a quick revision of the Chapter thereby helping you to enhance subject knowledge. Have a glance at the MCQ of Chapter 8 Physics Class 12 and cross-check your answers during preparation.
I. Choose the correct answer
Question 1.
If \(\vec {E}\) and \(\vec {B}\) represent electric and magnetic field vectors of the electromagnetic wave, the direction of propagation of electromagnetic wave is along
(a) \(\vec {E}\)
(b) \(\vec {B}\)
(c) \(\vec {B}\) × \(\vec {E}\)
(d) \(\vec {E}\) × \(\vec {B}\)
Answer
Answer: (d) \(\vec {E}\) × \(\vec {B}\)
Question 2.
The ratio of contributions made by the electric field and magnetic field components to the intensity of an EM wave is
(a) c : 1
(b) c² : 1
(c) 1 : 1
(d) √c : 1
Answer
Answer: (c) 1 : 1
Question 3.
A charged particle oscillates about its mean equilibrium position with a frequency of 109 Hz. The electromagnetic waves produced will not
(a) have a frequency of 109 Hz.
(b) have a frequency of 2 × 109 Hz.
(c) have a wavelength of 0.3 m.
(d) fall in the region of radio waves.
Answer
Answer: (b) have a frequency of 2 × 109 Hz.
Question 4.
The source of electromagnetic waves can be a charge
(a) moving with a constant velocity.
(b) moving in a circular orbit.
(c) at rest.
(d) none of these.
Answer
Answer: (b) moving in a circular orbit.
Question 5.
A plane electromagnetic wave of frequency 25 MHz travels in free space along the x-direction. At a particular point in space and time, the electric vector is \(\vec {E}\) = 6.3 Vm-1\(\hat {j}\). Calculate \(\vec {B}\) at
this point.
(a) 2.1 × 10-8 T
(b) 1.2 × 10-8 T
(c) 1.9 × 10-8 T
(d) 0.21 × 10-8T
Answer
Answer: (a) 2.1 × 10-8 T
Question 6.
What physical quantity is the same for X-rays of wavelength 10-10 m, red light of wavelength 680 nm and radio waves of wavelength 500 m?
(a) Wavelength
(b) Frequency
(c) Speed
(d) None of these.
Answer
Answer: (c) Speed
Question 7.
In an electromagnetic wave in free space, the root mean square value of the electric field is Erms = 6 V m-1. The peak value of the magnetic field is:
(a) 2.83 × 10-8 T
(b) 0.70 × 10-8 T
(c) 4.23 × 10-8 T
(d) 1.41 × 10-8 T
Answer
Answer: (a) 2.83 × 10-8 T
Question 8.
Arrange the following electromagnetic radiations per quantum in the order of increasing energy:
(A) Blue light
(B) Yellow light
(C) X-ray
(D) Radio wave
(a) A, B, C, D
(b) C, A, B, D
(c) B, A, D, C
(d) D, B, A, C
Answer
Answer: (d) D, B, A, C
Question 9.
A radiation of energy ‘E’ falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (c = Velocity of light)
(a) 2E/c
(b) 2E/c²
(c) E/c²
(d) E/c
Answer
Answer: (a) 2E/c
Question 10.
Match List -I (Electromagnetic wave type) with List – II (Its association/application) and select the correct option from the choices given below the lists:
List I | List II |
(A) Infrared | (i) To treat muscular strain |
(B) Radio waves | (ii) For broadcasting |
(C) X-rays | (iii) To detect fracture in bones |
(D) Ultraviolet rays | (iv) Absorbed by the ozone layer of the atmosphere |
(a) A-iii, B-ii, C-i, D-iv
(b) A-i, B-ii, C-iii, D-iv
(c) A-iv, B-iii, C-ii, D-i
(d) A-i, B-ii, C-iv, D-iii
Answer
Answer: (b) A-i, B-ii, C-iii, D-iv
II. Fill in the blanks
Question 1.
The conduction current is same as …………………. whether the source is ac or dc.
Answer
Answer: Displacement current
Question 2.
The current that flows inside a capacitor is ………………. current.
Answer
Answer: Displacement
Question 3.
An oscillating charge particle radiates ……………….
Answer
Answer: EM wave
Question 4.
EM waves are …………….. in nature.
Answer
Answer: Transverse
Question 5.
EM waves travel with a speed …………………
Answer
Answer: 3 × 108 m s-1
Question 6.
Human body radiates ………………… of EM spectrum.
Answer
Answer: IR radiation
Question 7.
EM waves transport both ………………… and ………………..
Answer
Answer: Energy, momentum
Question 8.
EM waves are produced by ………………… charsed particles.
Answer
Answer: Accelerated
Question 9.
In terms of permittivity (ε0) of free space and permeability (µ0) of free space the velocity of EM wave is ………………..
Answer
Answer: c = \(\frac { 1 }{\sqrt{µ_0ε_0}}\)
Question 10.
The ratio of velocities of light waves of wavelengths 400 nm and 800 nm in vacuum is ………………..
Answer
Answer: 1 : 1
Question 11.
For an EM wave the electric field along the X-axis is given by Ex = E0 sin (kz – ωt) then magnetic field is given by ……………….
Answer
Answer: By = B0 sin (kz – ωt)
Question 12.
The maximum value of electric field (E0) and maximum value of magnetic field (B0) in EM wave are related as ………………
Answer
Answer: c = E0/B0
Question 13.
The energy of EM wave is divided …………….. amongst the electric and the magnetic field.
Answer
Answer: Equally
Question 14.
Shorter the wavelength of an electromagnetic wave ………………….. energy it carries.
Answer
Answer: More
Question 15.
The orderly distribution of electromagnetic radiations according to their frequency or wavelength is termed as ……………….. spectrum.
Answer
Answer: Electromagnetic
Question 16.
………………. are used as a diagnostic tool.
Answer
Answer: X-rays
Question 17.
For Sterilisation ……………….. rays are used.
Answer
Answer: Ultraviolet
Question 18.
For looking through haze ………………… are used.
Answer
Answer: Infrared
Question 19.
………………. are used for cooking.
Answer
Answer: Microwaves
Question 20.
Waves used to transmit cellular telephone message are ………………..
Answer
Answer: Microwaves
Question 21.
To study structure of crystals ……………….. are used.
Answer
Answer: X-rays
Question 22.
Human eye can detect ……………….. part of electromagnetic spectrum.
Answer
Answer: visible
Question 23.
To treat cancer and tumour in radiography ………………… rays are used.
Answer
Answer: y-rays
Question 24.
During the propagation of an EM wave in a medium electrical energy density is ………………….. to magnetic energy density.
Answer
Answer: Equal
Question 25.
For an EM wave propagating along x-axis Emax = 30 Vm-1, the maximum value of magnetic field is ………………..
Answer
Answer: 10-7T
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