# CBSE Class 12 Physics Electromagnetic Waves MCQs

## MCQ for Class 12 Physics Electromagnetic Waves

Class 12 Physics students should refer to the following multiple-choice questions with answers for Electromagnetic Waves in standard 12. These MCQ questions with answers for Grade 12 Physics will come in exams and help you to score good marks

### Electromagnetic Waves MCQ Questions Class 12 Physics with Answers

Question: The electromagnetic waves do not transport
(a) energy
(b) charge
(c) momentum
(d) information

Question: The polarisation of electromagnetic wave is in
(a) the directions of electric and magnetic field
(b) the directions of electric field
(c) the direction of magnetic field
(d) can not be polarized

Question: The current in the electric circuit which arises due to flow of electrons in the connecting wires of the circuit in a defined closed path is called
(a) alternating current
(b) direct current
(c) conduction current
(d) displacement current

Question: If a variable frequency ac source connected to a capacitor then with decrease in frequency, the displacement current will
(a) increase
(b) decrease
(c) remain constant
(d) first decrease then increase

Question: Displacement current goes through the gap between the plates of a capacitor when the charge on the capacitor
(a) is changing with time
(b) decreases
(c) does not change
(d) decreases to zero

Question: An electron oscillating with a frequency of 3 × 106 Hz, would generate
(a) X-rays
(b) ultraviolet rays
(d) microwaves

Question: Select the wrong statement. EM waves
(a) are transverse in nature.
(b) travel in free space at a speed of light.
(c) are produced by accelerating charges.
(d) travel in all media with same speed.

Question: Which of the following has/have zero average value in a plane electromagnetic wave?
(a) Both magnetic and electric field
(b) Electric field only
(c) Magnetic energy
(d) Electric energy

Question: According to Maxwell’s hypothesis, a changing electric field gives rise to
(a) an e.m.f
(b) electric displacement current
(c) magnetic field

Question: An electromagnetic wave propagating along north has its electric field vector upwards. Its magnetic field vector point towards
(a) north
(b) east
(c) west
(d) downwards

Question: The current in the electric circuit which arises due to flow of electrons in the connecting wires of the circuit in a defined closed path is called
(a) alternating current
(b) direct current
(c) conduction current
(d) displacement current

Question: 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

Question: If a variable frequency ac source connected to a capacitor then with decrease in frequency, the displacement current will
(a) increase
(b) decrease
(c) remain constant
(d) first decrease then increase

Question: Displacement current goes through the gap between the plates of a capacitor when the charge on the capacitor
(a) is changing with time
(b) decreases
(c) does not change
(d) decreases to zero

Question: The displacement current was first postulated by
(a) Maxwell
(b) Marconi
(c) Ampere
(d) Hertz

Question: Ampere’s circuital law holds good for
(a) conduction current
(b) displacement current
(c) both (a) and (b)
(d) None of these

Question: When radio waves passes through ionosphere, phase difference between space current and capacitive displacement current is

Question: Displacement current is
(a) continuous when electric field is changing in the circuit
(b) continuous when magnetic field is changing in the circuit
(c) continuous in both types of fields
(d) continuous through wires and resistance only

Question: The velocity of all radio waves in free space is 3 × 108 m/s. The frequency of a radio wave of wavelength 150m is
(a) 20 kHz
(b) 2 kHz
(c) 2 MHz
(d) 1 MHz

Question: Maxwell’s equation describe the fundamental law of
(a) electricity
(b) magnetism
(c) mechanics
(d) both (a) and (b)

Question: The polarisation of electromagnetic wave is in
(a) the directions of electric and magnetic field
(b) the directions of electric field
(c) the direction of magnetic field
(d) can not be polarized

Question: According to Maxwell’s hypothesis, a changing electric field gives rise to
(a) an e.m.f
(b) electric displacement current
(c) magnetic field

Question: Electromagnetic wave consists of periodically oscillating electric and magnetic vectors
(a) in mutually perpendicular planes but vibrating with a phase difference of π
(b) in mutually perpendicular planes but vibrating with a phase difference of π/2
(c) in randomly oriented planes but vibrating in phase
(d) in mutually perpendicular planes but vibrating in phase

Question: An electromagnetic wave propagating along north has its electric field vector upwards. Its magnetic field vector point towards
(a) north
(b) east
(c) west
(d) downwards

Question: The electromagnetic waves
(a) travel with the speed of sound
(b) travel with the same speed in all media
(c) travel in free space with the speed of light
(d) do not travel through a medium

Question: Which of the following type of radiations are radiated by an oscillating electric charge?
(a) Electric
(b) Magnetic
(c) Thermoelectric
(d) Electromagnetic

Question: The absorption of radio waves by the atmosphere depends upon
(a) their velocities
(b) their frequencies
(c) their distance from the transmitter
(d) None of these

Question: If the frequency of EM radiations is halved then the energy of EM radiation will become
(a) double
(b) remains unchanged
(c) becomes half
(d) becomes one fourth

Question: The electromagnetic waves do not transport
(a) energy
(b) charge
(c) momentum
(d) information

Question: The amplitudes of electric and magnetic fields related to each other are
(a) E0 : B0
(b) E0 : cB0
(c) E0 : B0/c
(d) E0 : c/B0

Question: Microwaves are electromagnetic waves with frequency in the range of
(a) Micro hertz
(b) Giga hertz
(c) Mega hertz
(d) Hertz

Question: The speed of electromagnetic wave is same for
(a) odd frequencies
(b) even frequencies
(c) all frequencies
(d) all intensities

Question: A plane electromagnetic wave is incident on a material surface. If the wave delivers momentum p and energy E, then
(a) p : 0, E : 0
(b) p ≠ 0, E ≠ 0
(c) p ≠ 0, E : 0
(d) p : 0, E ≠ 0

Question: We consider the radiation emitted by the human body. Which one of the following statements is true?
(a) The radiation emitted is in the infrared region.
(b) The radiation is emitted only during the day.
(c) The radiation is emitted during the summers and absorbed during winters.
(d) The radiation is emitted lies in the ultraviolet region and hence is not visible.

Question: The decreasing order of wavelength of infrared,microwave, ultraviolet and gamma rays is
(a) microwave, infrared, ultraviolet, gamma rays
(b) infrared, microwave, ultraviolet, gamma rays
(c) gama rays, ultraviolet, infrared, microwaves
(d) microwaves, gamma rays, infrared, ultraviolet

Question: X-rays, gamma rays and microwaves travelling in vacuum have
(a) same wavelength but different velocities
(b) same frequency but different velocities
(c) same velocity but different wavelength
(d) same velocity and same frequency

Question: Radio waves diffract around building, although light waves do not. The reason is that radio waves
(a) travel with speed larger than c
(b) have much larger wavelength than light
(c) are not electromagnetic waves
(d) None of these

Question: Microwaves are detected by
(a) bolometer
(b) point contact diodes
(c) thermopiles
(d) the eye

Question: Which of the following electromagnetic waves has the longest wavelength?
(a) uv-rays
(b) Visible light
(d) Microwaves

Question: Which of the following is of shortest wavelength?
(a) X-rays
(b) γ-rays
(c) Microwaves

Question: The range of wavelength of visible light is
(a) 10 Å to 100 Å
(b) 4000 Å to 8000 Å
(c) 8000 Å to 10,000 Å
(d) 10,000 Å to 15,000 Å

Question: Which of the following is not electromagnetic waves?
(a) Cosmic rays
(b) Gamma rays
(c) γ-rays
(d) X-rays

Question: Which of the following electromagnetic radiations have the smallest wavelength?
(a) Ultraviolet waves
(b) X-rays
(c) γ-rays
(d) Microwaves

Question: Which of the following rays has minimum frequency?
(a) U.V. ways
(b) X-rays
(c) γ-rays
(d) Infra-red rays

Question: An accelerated electron would produce
(a) γ-rays
(b) β-rays
(c) α-rays
(d) e.m. waves

Question: Which of the following is the infrared wavelength?
(a) 10–4 cm
(b) 10–5 cm
(c) 10–6 cm
(d) 10–7 cm

Question: The wavelength of X-ray is of the order of
(a) 1 metre
(b) 1 cm
(c) 1 micron
(d) 1 angstrom

Question: Radio waves of constant amplitude can be generated with
(a) rectifier
(b) filter
(c) F.E.T.
(d) oscillator

Question: Radio waves do not penetrate in the band of
(a) ionosphere
(b) mesosphere
(c) troposphere
(d) stratosphere

Question: What is the cause of “Green house effect”?
(a) Infrared rays
(b) Ultraviolet rays
(c) X-rays

Question: If vs, vx and vm are the speed of soft gamma rays, X-rays and microwaves respectively in vacuum, then
(a) vs > vx > vm
(b) vs < vx < vm
(c) vs > vx < vm
(d) vs : vx : vm

Question: The waves which are electromagnetic in nature are
(a) sound waves and light waves
(b) water waves and radio waves
(c) light waves and X-rays
(d) sound waves and water waves

Question: In electromagnetic spectrum, the frequencies y-rays, X-rays and ultraviolet rays are denoted by n1, n2 and n3 respectively then
(a) n1 > n2 > n3
(b) n1 < n2 < n3
(c) n1 > n2 < n3
(d) n1 < n2 > n3

Question: Ultraviolet spectrum can be studied by using a
(a) flint glass prism
(b) direct vision prism
(c) nicol prism
(d) quartz prism

Question: The ozone layer in the atmosphere absorbs
(b) only the visible light
(c) only the γ-rays
(d) X-rays and ultraviolet rays

Question: Which one of the following has the maximum energy?
(b) Infrared rays
(c) Ultraviolet rays
(d) Micro waves

Question: Which one of the following has the shortest wavelength?
(a) Infrared rays
(b) Ultraviolet rays
(c) Microwaves
(d) Gamma rays

Question: When electromagnetic waves enter the ionised layer of ionosphere, then the relative permittivity i.e. dielectric constant of the ionised layer
(a) does not change
(b) appears to increase
(c) appears to decrease
(d) sometimes appears to increase and sometimes to decrease

Question: Ultraviolet rays coming from sun are absorbed by
(a) troposphere
(b) ionosphere
(c) stratosphere
(d) mesosphere

Question: The EM waves when travel into different media gets
(a) refracted
(b) transmitted
(c) reflected
(d) emitted

Question : The oscillating electric and magnetic vectors of an electromagnetic wave are oriented along
(a) the same direction but differ in phase by 90°
(b) the same direction and are in phase
(c) mutually perpendicular directions and are in phase
(d) mutually perpendicular directions and differ in phase by 90°

Question : Displacement current is
(a) continuous when electric field is changing in the circuit
(b) continuous when magnetic field is changing in the circuit
(c) continuous in both types of fields
(d) continuous through wires and resistance only

Question : In an electromagnetic wave, the electric and magnetic fields are 100 V m–1 and 0.265 A m–1. The maximum energy flow is
(a) 26.5 W/m2
(b) 36.5 W/m2
(c) 46.7 W/m2
(d) 765 W/m2

Question : Which of the following electromagnetic waves has the longest wavelength?
(a) uv-rays
(b) Visible light
(d) Microwaves

Question : The range of wavelength of visible light is
(a) 50 Å to 500 Å
(b) 4000 Å to 8000 Å
(c) 9000 Å to 25,000 Å
(d) 15,000 Å to 25,000 Å

Question : The wavelength of X-ray is of the order of
(a) 1 metre
(b) 1 cm
(c) 1 micron
(d) 1 angstrom

Question : Radio waves do not penetrate in the band of
(a) ionosphere
(b) mesosphere
(c) troposphere
(d) stratosphere

Question : What is the cause of “Green house effect”?
(a) Infrared rays
(b) Ultraviolet rays
(c) X-rays

Question : The waves used in telecommunication are
(a) IR
(b) UV
(c) Microwave
(d) Cosmic rays

Question : The electromagnetic radiation used in food processing sterilizing agent is
(a) microwaves
(b) UV rays
(c) gamma rays

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