MCQ Questions for Class 12 Physics Chapter 8 Electromagnetic Waves with Answers

  

Electromagnetic Waves Class 12 MCQs Questions with Answers

Question 1.
The dimensional formula of E⃗  is:
(a)[MLT-2A-1]
(b) [MLT-3A-1]
(c) [MLT-2A-2]
(d) None of these

Answer

Answer: (b) [MLT-3A-1]

---

Question 2.
The dimensional formula of is:
(a) [MLT-2A-1]
(b) [ML0T-2A-1]
(c) [ML0T-3A-1]
(d) None of these

Answer

Answer: (b) [ML0T-2A-1]

---

Question 3.
Which of the following has the dimensions of current?
(a) ε0 E⃗ .dt→
(b) µ0 E⃗ .dt→
(c) B⃗ .dl→µ0
(d) B⃗ .dl→ε0

Answer

Answer: (c) B⃗ .dl→µ0

---

Question 4.
Which of the following has the dimensions of charge?
(a) ε0E⃗ ds→
(b) µ0 E⃗ .ds→
(c) ε0µ0 E⃗ .ds→
(d) µ0ε0 E⃗ .ds→

Answer

Answer: (a) ε0E⃗ ds→

---

Question 5.
Maxwell’s equation involving ddt B⃗  is obtained-from:
(a) Ampere’s law
(b) Gauss’s law
(c) Faraday’s law
(d) Biot-Savart’s law

Answer

---

Question 6.
The dimensions of E⃗ , dl→ are identical to that of:
(a) potential
(b) charge
(c) current
(d) None of these

Answer

Answer: (a) potential

---

Question 7.
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 these

Answer

Answer: (b) Ampere’s law

---

Question 8.
Choose the wave relevant to telecommunication :
(a) ultraviolet
(b) infrared
(c) microwave
(d) visible light

Answer

Answer: (c) microwave

---

Question 9.
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

Answer: (a) 3 × 105 kms-1

---

Question 10.
Which of the following EMW has highest wavelength?
(a) X-ray
(b) ultraviolet rays
(c) infrared rays
(d) microwaves

Answer

Answer: (c) infrared rays

---

Question 11.
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

Answer: (b) the Varying electric field

---

Question 12.
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

Answer: (a) equal to conduction current

---

Question 13.
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

Answer: (c) accelerated or decelerated charge only

---

Question 14.
Who first demonstrated the existence of em waves?
(a) Hertz
(b) Maxwell
(c) Ampere
(d) Faraday

Answer

Answer: (a) Hertz

---

Question 15.
If B⃗  is the magnetic field vector and E⃗  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 = EB
(b) c = BE
(c) c = BE
(d) c = 1EB

Answer

Answer: (a) c = EB

---

Question 16.
The dimensions of E/Bare same as that of:
(a) charge
(b) current
(c) velocity
(d) acceleration

Answer

Answer: (c) velocity

---

Question 17.
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

Answer: (c) Modified Ampere’s law

---

Question 18.
The existence of EMW was experimentally established by :
(a) Sir S. C. Bose
(b) Maxwell
(c) Marconi
(d) Hertz

Answer

Answer: (a) Sir S. C. Bose

---

Question 19.
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

Answer: (c) Wavelength is halved and the frequency remains unchanged

---

Question 20.
Frequency of a wave is 6 × 1015. Hz. The wave is :
(a) Radiowave
(b) Microwave
(c) X-ray
(d) Ultra violet

Answer

Answer: (d) Ultra violet

---

Question 21.
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

Answer: (d) Electromagnetic waves travel with the same speed in all media

---

Question 22.
If ue and um arc the electric and magnetic field densities in an electromagnetic wave, then (c is the speed of light):
(a) ue = um
(b) ue = c um
(c) ue = umc
(d) None of these

Answer

Answer: (a) ue = um

---

Question 23.
Solar radiation is :
(a) transverse EMW
(b) longitudinal EMW
(c) both (a) and (b)
(d) None of these

Answer

Answer: (a) transverse EMW

---

Question 24.
Ampere’s circuital law was modified by:
(a) Laplace
(b) Gauss
(c) Maxwell
(d) Hertz

Answer

Answer: (c) Maxwell

---

Question 25.
Light Year is the unit of:
(a) distance
(b) time
(c) energy
(d) intensity of light

Answer

Answer: (a) distance

---