Physics - Electromagnetic Waves - Quiz-3

Displacement current is :

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continuous when the electric field is changing in the circuit
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continuous when the magnetic field is changing in the circuit
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continuous in both types of fields
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continuous through wires and resistance only

A radiowave has a maximum magnetic field induction of $10^{- 4}$ T on arrival at a receiving antenna. The maximum electric field intensity of such a wave is

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zero
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$3 \times 10^{4} V / m$
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$5.8 \times 10^{- 9} V / m$
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$3.3 \times 10^{13} V / m$

A capacitor is having a capacity of 2 pF. The electric potential across the capacitor is changing with a value of $10^{12}$ V/s. The displacement current is :

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2 A
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3 A
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6 A
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9 A

The shortest wavelength is for

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$γ$ -rays
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X-rays
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ultraviolet rays
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microwaves

An accelerated charge :

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emits an electromagnetic wave
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does not emit electromagnetic wave
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produces a gravitational field
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None of these

The electromagnetic radiations are in descending order of wavelength in the following sequences :

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infra-red waves, radio waves, X-rays, visible light rays
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Radio-waves, infra-red waves, visible light rays, X-rays
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Radio waves, visible light rays, infra-red waves, X-rays
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X-rays, visible light rays, infra-red wave, radio-waves

X-rays and $γ$ -rays are both electromagnetic waves, which one of the following statements is true?

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in general, X-rays have a larger wavelength than that of $γ$ -rays
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X-rays have a smaller wavelength than that of $γ$ -rays
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$γ$ -rays have smaller frequency than that of X-rays
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wavelength and frequency of X-rays are both larger than those of $γ$ -rays.

Which of the following are not electromagnetic waves?

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cosmic rays
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gamma rays
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microwaves
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X-rays

The frequencies of X-rays, $γ$ -rays and ultraviolet rays are respectively a, b and c. Then :

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a < b, b < c
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a > b, b > c
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a > b, b > a
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a < b, b > c

A plane electromagnetic wave of frequency 40 MHz travels in free space in the x-direction. At some point and at some instant, the electric field $\vec{E}$ has its maximum value of 750 N/C in y-direction. The wavelength of the wave is

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3.5 m
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5.5 m
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7.5 m
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9.5 m

The waves used in telecommunication are

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infrared
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visible light
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microwaves
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ultraviolet rays

Statement I: Light can travel in vacuum but sound cannot do so.
Statement II Light is an electromagnetic wave and sound is a mechanical wave.

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If both Statement - I and Statement - II are true, and Statement - II is the correct explanation of Statement - I
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If both Statement - I and Statement - II are true but Statement - II is not the correct explanation of Statement - I.
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If Statement - I is true but Statement - II is false.
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If Statement - I is false but Statement - II is ture.

The wave impedance of free space is

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0 $Ω$
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376.6 $Ω$
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1883 $Ω$
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3776 $Ω$

The frequency 1057 MHz of radiation arising from two close energy levels in hydrogen belongs to

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radio waves
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infrared waves
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micro waves
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$γ$ -rays

X-rays are not used for radar purposes, because they are not

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reflected by target
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partly absorbed by the target
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electromagnetic waves
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completely absorbed by the target

The energy of the X-rays photon is 3.3 $\times 10^{- 16}$ J. Its frequency is :

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$2 \times 10^{19} H z$
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$5 \times 10^{18} H z$
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$5 \times 10^{17} H z$
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$5 \times 10^{16} H z$

If a source is transmitting an electromagnetic wave of frequency $8.2 \times 10^{6} H z$ , then the wavelength of the electromagnetic wave transmitted from the source will be:

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36.6 m
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40.5 m
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42.3 m
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50.9 m

A plane electromagnetic wave $E_{z} = 100 \cos (6 \times 10^{8} t + 4 x) V / m$ propagates in a medium of dielectric constant

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(1) 5
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(2) 0
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(3) 2.4
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(4) 0

If $μ_{0}$ be the permeability and $K_{0}$ the dielectric constant of a medium, its refractive index is given by

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$\frac{1}{\sqrt{μ_{0} K_{0}}}$
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$\frac{1}{μ_{0} K_{0}}$
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$\sqrt{K_{0}}$
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$μ_{0} K_{0}$

If $ε_{0} a n d μ_{0}$ represent the permittivity and permeability of vacuum and $ε a n d μ$ represent the permittivity and permeability of the medium, the refractive index of the medium is given by

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$\sqrt{\frac{ε_{0} μ_{0}}{ε μ}}$
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$\sqrt{\frac{ε μ}{ε_{0} μ_{0}}}$
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$\sqrt{\frac{ε}{μ_{0} ε_{0}}}$
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$\sqrt{\frac{μ_{0} ε_{0}}{ε}}$

The magnetic field between the plates of radius 12 cm separated by a distance of 4 mm of a parallel plate capacitor of capacitance 100 pF along the axis of plates having conduction current of 0.15 A is

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zero
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1.5 T
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15 T
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0.15 T

A flood light is covered with a fitter that transmits red light. The electric field of the emerging beam is represented by a sinusoidal plane wave

$E_{x} = 36 \sin (1.20 \times 10^{7} z - 3.6 \times 10^{15} t) V / m$

The average intensity of beam in W/ $m^{2}$ will be

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6.88
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3.44
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1.72
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0.86

A larger parallel plate capacitor, whose plates have an area of 1 $m^{2}$ are separated from each other by 1 mm, is being charged at a rate of 25.8 V/s. If the plates has dielectric constant 10, then the displacement current at this instant is

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25 $μ A$
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11 $μ A$
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2.2 $μ A$
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1.1 $μ A$

A parallel plate capacitor with plate area A and separation between the plates d, is charged by a constant current i. Consider a plane surface of area A/2 parallel to the plates and drawn symmetrically between the plates. The displacement current through this area is

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i
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i/2
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i/4
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i/8

The sun delivers $10^{4} W / m^{2}$ of electromagnetic flux to the earth's surface. The total power that is incident on a roof of dimensions (10 $\times$ 10) $m^{2}$ will be

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$10^{4}$ W
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$10^{5} W$
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$10^{6} W$
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$10^{7} W$

The wave of wavelength 5900 $\overset{0}{A}$ emitted by any atom or molecule must have some finite total length which is known as coherence length. For sodium light, this length is 2.4 cm. The number of oscillations in this length will be

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$4.068 \times 10^{8}$
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$4.068 \times 10^{4}$
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$4.068 \times 10^{6}$
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$4.068 \times 10^{5}$

The transmitting antenna of a radio station is mounted vertically. At a point 10 km due north of the transmitter, the peak electric field is $10^{- 3}$ V/m. The amplitude of the radiated magnetic field is

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$3.33 \times 10^{- 10} T$
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$3.33 \times 10^{- 12} T$
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$10^{- 3} T$
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$3 \times 10^{5} T$

A circular ring of radius r is placed in a homogeneous magnetic field perpendicular to the plane of the ring. The field B changes with time according to the equation B = Kt, where K is a constant and t is the time. The electric field in the ring is

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$\frac{K r}{4}$
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$\frac{K r}{3}$
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$\frac{K r}{2}$
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$\frac{K}{2 r}$

A plane EM-wave of wave intensity of 10 $W / m^{2}$ strikes a small mirror of area 20 $c m^{2}$ , held perpendicular to the approaching wave. The radiation force on the mirror will be

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$6.6 \times 10^{- 11} N$
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$1.33 \times 10^{- 11} N$
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$1.33 \times 10^{- 10} N$
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$6.6 \times 10^{- 10} N$

In a region of free space, the electric field at some instant of time is $\vec{E} = (80 \hat{i} + 32 \hat{j} - 64 \hat{k})$ V/m and the magnetic field is $\vec{B} = (0.2 \vec{i} + 0.08 \hat{j} + 0.29 \hat{k}) μ T$ . The Poynting vector for these fields is-

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(1) $- 11.52 \hat{i} + 28.8 \hat{j}$
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(2) $- 28.8 \hat{i} + 11.52 \hat{i}$
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(3) $28.8 \hat{i} - 11.52 \hat{j}$
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(4) $11.52 \hat{i} - 28.8 \hat{j}$

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Practice Physics Quiz Questions and Answers

0:0:1

Practice Physics Quiz Questions and Answers

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