Electromagnetic Waves — practice questions

155 curated practice questions from Electromagnetic Waves (Physics Class 12, CBSE) — 37 medium, 116 easy, 2 hard. Every question includes the final answer free; step-by-step worked solutions with a free account.

• The electric field E associated with an electromagnetic wave is represented by E _ y = E _ 0 ( kx - t ) Which of the…
• Assertion (A): Electromagnetic radiations exert pressure. Reason (R): Electromagnetic waves carry both momentum and…
• If a source is transmitting electromagnetic waves of frequency 8.2 10 6 Hz, the wavelength of an electromagnetic wave…
• Welders wear special glass goggles or face masks with glass windows to protect their eyes from:
• Assertion (A): Electromagnetic waves are transverse in nature. Reason (R): The electric and magnetic fields of an e.m…
• Displacement current goes through the gap between the plates of a capacitor when the charge on the capacitor
• Which of the following electromagnetic waves has photons of largest momentum?
• Light with an energy flux of 18 W/cm 2 falls on a non-reflecting surface at normal incidence. The pressure exerted on…
• An electromagnetic wave is propagating along x -axis. At x = 1 m and t = 10 s, its electric vector | E |=6 ~V / m then…
• Assertion (A): X-rays are produced when slow moving electrons are stopped by a metal target of high atomic number…
• The correct option, if speeds of gamma rays, X-rays and microwaves are v g , u x and v m respectively will be:
• Name the electromagnetic waves also known as heat waves .
• The electric field of a plane electromagnetic wave varies with time of amplitude 2 V m –1 propagating along z -axis…
• When a low flying aircraft passes overhead, we sometimes notice a slight shaking of the picture on our TV screen. This…
• The ultra high frequency band of radiowaves in electromagnetic wave is used as in
• Welders wear special glass goggles or face masks with glass windows to protect their eyes from radiations produced by…
• A parallel plate capacitor has capacitance C = 62 pF and carries a displacement current of I_d = 0.15 A . The rate of…
• Assertion (A): EM waves do not require a medium for their propagation. Reason (R): EM waves are transverse waves.
• Waves in the decreasing order of their wavelengths are:
• The electric and the magnetic fields, associated with an e.m. wave, propagating along the + z-axis, can be represented…
• An electromagnetic wave of frequency u = 3 MHz passes from vacuum into a dielectric medium with permittivity e = 4. Then
• Light with an energy flux of 18 W cm –2 falls on a non-reflecting surface at normal incidence. If the surface has an…
• The magnetic field of an electromagnetic wave is represented as B _ x = B _ 0 ( ky - t ) . It means that the wave…
• Which of the following radiations has the highest frequency?
• Electromagnetic waves travel in a medium that has relative permeability 1.3 and relative permittivity 2.14. Then the…
• The electric and magnetic fields of electromagnetic waves are
• A plane electromagnetic wave of frequency 25 MHz travels in free space along the x -direction. At a particular point in…
• Assertion (A): When a charged particle moves in a circular path, it produces an electromagnetic wave. Reason (R)…
• According to Maxwell's hypothesis, a changing electric field gives rise to
• X-rays, gamma rays and microwaves travelling in vacuum have
• Electromagnetic waves with wavelength 10 nm are called:
• The electric field of an electromagnetic wave travelling through vacuum is given by the equation E = E 0 sin ( kx – ω t…
• Which one of the following electromagnetic radiation has the least wavelength?
• The electric field part of an electromagnetic wave in a medium is represented by E x = 0, E_ y =2.5 ~N C [ (2 10^ 6 rad…
• Choose the correct option related to wavelengths ( ) of different parts of electromagnetic spectrum.
• We consider the radiation emitted by the human body. Which one of the following statements is true?
• The given diagram exhibits the relationship between the wavelength of the electromagnetic waves and the energy of…
• If represent electric and magnetic field vectors of the electromagnetic wave, then the direction of propagation of…
• A microwave and an ultrasonic sound wave have the same wavelength. Their frequencies are in the ratio (approximately)
• The charge on a parallel plate capacitor varies as q = q 0 cos2πυ t . The plates are very large and close together…
• The amplitude of the magnetic field of a harmonic electromagnetic wave in vacuum is B 0 = 510 nT. The amplitude of the…
• We consider the radiation emitted by the human body. Which one of the following statements is true?
• The decreasing order of wavelength of infrared, microwaves, ultraviolet and -rays is
• The dimensions of ( _ 0 _ 0 )^ -1 / 2 are
• Assertion(A): Out of Infrared and radio waves, the radio waves show more diffraction effect. Reason (R): Radio waves…
• The phase difference between electric field E and magnetic field B in an electromagnetic wave propagating along z -axis…
• Which of the following rays is not an electromagnetic wave?
• Which of the following has/have zero average value in a plane electromagnetic wave?
• The photon energy in units of eV for electromagnetic waves of wavelength 2 cm is
• A plane electromagnetic wave is incident on a material surface. The wave delivers momentum p and energy E . Then
• Which of the following electromagnetic wave is used in high precision application like LASIK eye surgery?
• Which one of the following is the property of a monochromatic, plane electromagnetic wave in free space?
• Maxwell in his famous equations of electromagnetism introduced the concept of
• There are three wavelengths: 10 -8 m, 10 -2 m, 10 8 m. Their respective names are:
• Magnitude of the electric and the magnetic fields in an plane electromagnetic wave are related by
• X-rays are more harmful to human beings than ultraviolet radiations because X-rays-
• Which one of the following has the highest frequency?
• E and B represent the electric and the magnetic field of an electromagnetic wave respectively. The direction of…
• A plane electromagnetic wave travels in vacuum along z -direction. If the frequency of the wave is 40 MHz then its…
• The source of electromagnetic waves can be charge, when
• The temperature of an object that emits electromagnetic radiation must be
• Which of the following rays coming from the Sun plays an important role in maintaining the Earth's warmth?
• In four regions I, II, III and IV, the magnetic field is given by: B _ y = B _0 kz B _ y = B _0 kz B _ y = B _0 ( kz …
• The amplitude of an electromagnetic wave in vacuum is doubled with no other changes made to the wave. As a result of…
• Radiations of intensity 0.5 W m –2 are striking a metal plate. The pressure on the plate is
• The electric field part of an electromagnetic wave in vacuum is E = 3.1 N C ^ -1 [(1.8 rad m ^ -1 ) y + (5.4 10^ 8 rad…
• The energy of the e.m. waves is of the order of 15 keV. To which part of the spectrum does it belong?
• Out of the following options which one can be used to produce a propagating electromagnetic wave?
• An em wave is propagating in a medium with a velocity V =V i . The instantaneous oscillating electric field of this em…
• The electric field part of an electromagnetic wave in a medium is represented by E x = 0; E_ y =2.5 N C [ (2 10^ 6 rad…
• A capacitor is charged by a battery. Between the plates, during process of charging:
• The electric field intensity produced by the radiations coming from 100 W bulb at 3 m distance is E . The electric…
• Which of the following will deflect in the electric field?
• Assertion (A): The earth without its atmosphere would be inhospitably cold. Reason (R): All heat would escape in the…
• Which of the following statement is false for the properties of electromagnetic waves?
• The electric field in space between the plates of a parallel plate capacitor (each of area 2.5 10^ -3 ~m ^ 2 ) is…
• Assertion (A): In electromagnetic waves, electric field and magnetic field lines are perpendicular to each other…
• Which of the following electromagnetic radiations have the longest wavelength?
• All the known radiations from a big family of electromagnetic waves which stretch over a large range of wavelengths…
• A galaxy moves with respect to us so that sodium line of 589.0 nm is observed at 589.6 nm. The speed of the galaxy is
• The electromagnetic radiations used to kill germs in water purifiers are called:
• In the electromagnetic spectrum, what is the frequency corresponding to the radio wave region?
• Assertion (A): X-ray astronomy is possible only from satellites orbiting the earth. Reason (R): Efficiency of X-rays…
• The condition under which a microwave oven heats up a food item containing water molecules most efficiently is
• The amplitude of electric field in an electromagnetic wave in free space is 1000 Vm ^ -1 . The amplitude of the…
• Which of the following electromagnetic waves is used in medicine to destroy corner cells?
• The velocity of electromagnetic waves in free space is 3 10 8 ms -1 . The frequency of a radio wave of wavelength 150 m…
• An electromagnetic wave radiates outwards from a dipole antenna, with the amplitude of its electric field vector E 0 …
• The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating in…
• An electromagnetic wave propagating along north has its electric field vector upwards. Its magnetic field vector point…
• The refractive index and permeability of a medium are 1.5 and 5 × 10 –7 H m –1 respectively. The relative permittivity…
• The ratio of the magnitudes of the electric field and magnetic field of a plane electromagnetic wave is
• Assume a bulb of efficiency 2.5% as a point source. The peak values of electric and magnetic fields produced by the…
• Assertion (A): UV radiation causes photo-dissociation of ozone into O 2 and O, thus causing damage to the stratospheric…
• Which radiations are used in the treatment of muscles ache?
• In the question 62, the amplitude of magnetic field part of the given wave is
• A parallel plate capacitor with plate area A and separation between the plates d , is charged by a constant current I …
• Electromagnetic waves with frequency 1.0 10 18 Hz are known as:
• Assertion (A): Radiowaves can be polarised. Reason (R): Sound waves in air are longitudinal in nature.
• One requires 11 eV of energy to dissociate a carbon monoxide molecule into carbon and oxygen atoms. The minimum…
• The electric and magnetic fields in an electromagnetic wave are
• A plane electromagnetic wave of frequency 25 MHz travels in free space along x -direction. At a particular point in…
• The conduction current is same as displacement current when source is
• Which of the following are not electromagnetic waves?
• Which of the following physical quantities remain the same for X-ray, red light and radio waves when travelling through…
• Which one of the following correctly represents the change in wave characteristics (all in vacuum) from microwaves to…
• For a medium with permittivity E and permeability , the velocity of light is given by:
• In order to establish an instantaneous displacement current of 1 mA in the space between the plates of 2 µF parallel…
• The conduction current is the same as the displacement current when the source is:
• The pressure exerted by an electromagnetic wave of intensity I(Wm -2 ) on a non-reflecting surface is (c is the…
• The magnetic field of a beam emerging from a filter facing a flood light as given by B = 12 × 10 –8 sin (1.20 × 10 7 z…
• Which of the following electromagnetic waves has smaller wavelength?
• In an electromagnetic wave in free space, the root means square value of the electric field is E rms = 6 V/m. The peak…
• An electromagnetic wave of intensity I falls on a surface kept in vacuum and exerts radiation pressure P on it. Which…
• A radio can tune to any station in 7.5 MHz to 12 MHz band. The corresponding wavelength band is
• Electromagnetic waves of wavelength of the order of a few meters were first produced and detected in the laboratory by:
• Which of the following electromagnetic wave play an important role in maintaining the earth’s warmth or average…
• A plane electromagnetic wave is travelling in air in +x direction. At a particular moment, its electric field E is…
• Assertion (A): Dipole oscillations produce electromagnetic waves. Reason (R): Accelerated charge produces…
• Which of the following is not true for electromagnetic waves?
• The wavelength of light belongs to the ___________ part of the spectrum.
• In the case of linearly polarized light, the magnitude of the electric field vector
• In the four regions, I, II, III and IV, the electric fields are described as: Region I : E _ x = E _0 ( kz - t ) Region…
• A charged particle oscillates about its mean equilibrium position with a frequency of 10 9 Hz. The frequency of…
• The ratio of the amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating…
• Assertion (A): Sound waves cannot travel in a vacuum but light can travel in a vacuum. Reason (R): Sound waves are…
• The frequency of -rays, X-rays and ultraviolet rays are a, b and c respectively. Then,
• A plane electromagnetic wave propagating along x direction can have the following pairs of
• The waves used by artificial satellites for communication is
• Electromagnetic waves used as a diagnostic tool in medicine are
• The part of the spectrum of the electromagnetic radiation used to cook food is
• The first scientist who produced and observed electromagnetic waves of wavelengths in the range 25 mm 5 mm was:
• In an electromagnetic wave travelling in free space, the amplitude of magnetic field is 6.0 10^ -4 ~T . The amplitude…
• Which wavelength of the sun is used finally as electric energy?
• The ratio of contributions made by the electric field and magnetic field components to the intensity of an…
• Two towers on the top of two hills are 40 km apart. The line joining them passes 50 m above a hill halfway between the…
• In a travelling plane electromagnetic wave, which of the following have zero average value?
• For a wave propagating in a medium, identify the property that is independent of the others.
• Frequency of radiations arising from two close energy levels in hydrogen, known as lamb shift is 1057 MHz. This…
• A. Wavelength of microwaves is greater than that of ultraviolet rays. B. The wavelength of infrared rays is lesser than…
• The electric field associated with an e.m. wave in vacuum is given by E = i 40 ( z-6 10^ 8 t ) , where E, z and t are…
• About 6% of the power of a 100 W light bulb is converted to visible radiation. The average intensity of visible…
• The frequency of electromagnetic wave which is best suitable to observe a particle of radius 3 × 10 –4 cm is of the…
• The radiation pressure (in N/m 2 ) of the visible light is of the order of
• If v s , v x and v m are the speeds of gamma rays, X-rays and microwaves respectively in vacuum, then
• The electric field associated with an electromagnetic wave in vacuum is given by E =40 (kz-6 10^ 8 t ) i , where E , z…
• If v g , v X and v m are the speeds of gamma rays, X-rays and microwaves respectively in vacuum, then
• Assertion (A): The energy of X-ray photon is greater than that of light (visible) photon. Reason (R): X-ray photon in…
• The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is
• An electromagnetic radiation has an energy of 13.2 keV. Then the radiation belongs to the region of
• X-rays and g -rays of same energies are distinguished by their
• The dimensions of ( )^ -1 , where is permittivity and is permeability of a medium, are:
• A welder wears special glasses to protect his eyes mostly from the harmful effect of
• In an electromagnetic wave, the electric and magnetic fields are 100 V/m and 0.265 A/m. The maximum energy flow will be:
• Which of the following electromagnetic waves are known as 'heat waves'?

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