Electromagnetic waves Practice Test

12th Standard Physics — Electromagnetic waves: Online Practice Test

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The dimension of \(\frac{1}{\mu_o \epsilon_o}\) is

A.\([L T^{-1}]\) B.\([L^2 T^{-2}]\) C.\([L^{-1} T]\) D.\([L^{-2} T^2]\)

If the amplitude of the magnetic field is \(3 \times 10^{-6}\) T, then the amplitude of the electric field for an electromagnetic wave is

A.100 V m\(^{-1}\) B.300 V m\(^{-1}\) C.600 V m\(^{-1}\) D.900 V m\(^{-1}\)

Which of the following electromagnetic radiations is used for viewing objects through fog?

A.microwave B.gamma rays C.X-rays D.infrared

Which of the following is false for electromagnetic waves?

A.transverse B.non-mechanical waves C.longitudinal D.produced by accelerating charges

Consider an oscillator which has a charged particle oscillating about its mean position with a frequency of 300 MHz. The wavelength of electromagnetic waves produced by this oscillator is

A.1 m B.10 m C.100 m D.1000 m

The electric and the magnetic fields, associated with an electromagnetic wave, propagating along negative X axis can be represented by

A.\(\vec{E} = E_o \hat{i}, \vec{B} = B_o \hat{k}\) B.\(\vec{E} = E_o \hat{k}, \vec{B} = B_o \hat{j}\) C.\(\vec{E} = E_o \hat{i}, \vec{B} = B_o \hat{j}\) D.\(\vec{E} = E_o \hat{j}, \vec{B} = B_o \hat{i}\)

In an electromagnetic wave travelling in free space the rms value of the electric field is 3 V m\(^{-1}\). The peak value of the magnetic field is

A.\(1.414 \times 10^{-8}\) T B.\(1.0 \times 10^{-8}\) T C.\(2.828 \times 10^{-8}\) T D.\(2.0 \times 10^{-8}\) T

An e.m. wave is propagating in a medium with a velocity \(\vec{v} = v\hat{i}\). The instantaneous oscillating electric field of this e.m. wave is along +y-axis, then the direction of oscillating magnetic field of the e.m. wave will be along:

A.–y direction B.–x direction C.+z direction D.–z direction

If the magnetic monopole exists, then which of the Maxwell’s equation to be modified?

A.\(\oint \vec{E} \cdot d\vec{A} = \frac{Q_{enclosed}}{\epsilon_o}\) B.\(\oint \vec{B} \cdot d\vec{A} = 0\) C.\(\oint \vec{B} \cdot d\vec{l} = \mu_o i_c + \mu_o \epsilon_o \frac{d\Phi_E}{dt}\) D.\(\oint \vec{E} \cdot d\vec{l} = -\frac{d\Phi_B}{dt}\)

Q10

Fraunhofer lines are an example of _______ spectrum.

A.line emission B.line absorption C.band emission D.band absorption

Q11

Which of the following is an electromagnetic wave?

A.\(\alpha\) - rays B.\(\beta\) - rays C.\(\gamma\) - rays D.all of them

Q12

Which one of them is used to produce a propagating electromagnetic wave?

A.an accelerating charge B.a charge moving with constant velocity C.a stationary charge D.an uncharged particle

Q13

If \(E = E_o \sin[10^6 x - \omega t]\) be the electric field of a plane electromagnetic wave, the value of \(\omega\) is

A.\(0.3 \times 10^{-14}\) rad s\(^{-1}\) B.\(3 \times 10^{-14}\) rad s\(^{-1}\) C.\(0.3 \times 10^{14}\) rad s\(^{-1}\) D.\(3 \times 10^{14}\) rad s\(^{-1}\)

Q14

Which of the following is NOT true for electromagnetic waves?

A.it transports energy B.it transports momentum C.it transports angular momentum D.in vacuum, it travels with different speeds which depend on their frequency

Q15

The electric and magnetic fields of an electromagnetic wave are

A.in phase and perpendicular to each other B.out of phase and not perpendicular to each other C.in phase and not perpendicular to each other D.out of phase and perpendicular to each other

Q16

Which term did James Clerk Maxwell introduce to Ampere's circuital law to explain the production of magnetic fields by time-varying electric fields?

A.Conduction current B.Displacement current C.Eddy current D.Static current

Q17

What physical reality is implied by the Maxwell's second equation (Gauss's law for magnetism), which states that the surface integral of a magnetic field over a closed surface is zero?

A.Magnetic monopoles exist in pairs B.Isolated magnetic monopoles do not exist C.Magnetic field lines are discontinuous D.Magnetic field depends on time

Q18

In a vacuum, what is the mathematical relationship between the speed of light \(c\), the permittivity of free space \(\epsilon_0\), and the permeability of free space \(\mu_0\)?

A.\(c = \sqrt{\mu_0 \epsilon_0}\) B.\(c = \frac{1}{\mu_0 \epsilon_0}\) C.\(c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}\) D.\(c = \mu_0 \epsilon_0\)

Q19

If an electromagnetic wave is propagating along the positive z-direction and its electric field vector points along the x-axis, in which direction does the magnetic field vector oscillate?

A.Along the x-axis B.Along the y-axis C.Along the z-axis D.Opposite to the x-axis

Q20

What was the significant conclusion drawn from Heinrich Hertz's 1888 experiment regarding the receiver's orientation?

A.EM waves are longitudinal B.EM waves require a medium C.EM waves are transverse D.EM waves have infinite speed

Q21

Radio waves are primarily produced by which of the following physical processes?

A.Sudden stopping of high-speed electrons B.Accelerated motion of charges in conducting wires C.Transitions of radioactive nuclei D.Rotational transitions of molecules

Q22

Which type of electromagnetic radiation is extensively used in radar systems for aircraft navigation and speed detection of vehicles?

A.Infrared radiation B.Visible light C.Microwaves D.X-rays

Q23

Why are infrared radiations often referred to as 'heat waves'?

A.They have the highest frequency B.They are produced by hot bodies and molecules C.They are visible to the human eye D.They ionize atmospheric gases

Q24

Which constituent of the Earth's atmosphere is primarily responsible for absorbing harmful ultraviolet (UV) radiation from the Sun?

A.Nitrogen B.Oxygen C.Ozone D.Carbon dioxide

Q25

How are X-rays produced in a laboratory setting for medical applications?

A.By radioactive decay of nuclei B.By sudden stopping of high-speed electrons at a target C.By heating metals to high temperatures D.By passing current through a coil

Q26

Gamma rays are distinct from other electromagnetic waves because they originate from which source?

A.Transitions in the outermost electron shells B.Oscillating molecular dipoles C.Transitions of radioactive nuclei D.Vibrating hot solid bodies

Q27

What type of emission spectrum is obtained from incandescent solids and the light from a carbon arc?

A.Line emission spectrum B.Continuous emission spectrum C.Band emission spectrum D.Line absorption spectrum

Q28

The discrete dark lines observed in the solar spectrum, known as Fraunhofer lines, are examples of which type of spectrum?

A.Line emission spectrum B.Line absorption spectrum C.Band emission spectrum D.Continuous absorption spectrum

Q29

Calculate the refractive index of a medium if its relative permeability is 1.0 and its relative electrical permittivity (dielectric constant) is 2.25.

A.1.25 B.1.50 C.2.25 D.3.00

Q30

If an electromagnetic wave of energy \(U\) is incident on a surface and is completely absorbed, what is the magnitude of the linear momentum \(p\) imparted to the surface?

A.\(p = U \cdot c\) B.\(p = \frac{U}{c}\) C.\(p = \frac{2U}{c}\) D.\(p = \sqrt{U \cdot c}\)

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About this Electromagnetic waves test

This free online practice test covers Electromagnetic waves from the 12th Standard Physics (Samacheer Kalvi) syllabus. Choose the number of questions and an optional time limit, then answer and submit — everything is checked in your browser, with the correct answers and a worked explanation shown at the end. For the full solutions to every question in this set, see the solved MCQs page.

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