JEE Physics

Problem 2112

Who produced the electromagnetic waves first?
(A) Marconi
(B) Maxwell
(C) J.C. Bose
(D) Hertz

Narayan Hari

Numerade Educator

Problem 2113

The dimensional formula of $\mu_{0} \mathrm{E}_{0}$ is
(A) $L^{2} T^{-2}$
(B) $L^{-2} T^{2}$
(C) $\mathrm{L}^{1} \mathrm{~T}^{-1}$
(D) ${L}^{-1} \mathrm{~T}^{1}$

Narayan Hari

Numerade Educator

A plane electromagnetic wave is incident on a mater1al surface. The wave delivers momentum $P$ and energy $E$
(A) $\mathrm{P}=0, \mathrm{E} \neq 0$
(B) $\mathrm{P} \neq 0, \mathrm{E}=0$
(C) $P \neq 0, E \neq 0$
(D) $P=0, E=0$

Narayan Hari

Numerade Educator

Problem 2115

If $\mathrm{V}_{\mathrm{r}}, \mathrm{V}_{\mathrm{x}}$ and $\mathrm{V}_{\mathrm{m}}$ are the velocity of the $\gamma$ rays, $\mathrm{x}$ rays, micro waves respectively in space, then
(A) $\mathrm{V}_{\gamma}<\mathrm{V}_{\mathrm{x}}<\mathrm{V}_{\mathrm{m}}$
(B) $\mathrm{V}_{\mathrm{r}}=\mathrm{V}_{\mathrm{x}}=\mathrm{V}_{\mathrm{m}}$
(C) $\mathrm{V}_{\mathrm{r}}^{\prime}>\mathrm{V}_{\mathrm{x}}>\mathrm{V}_{\mathrm{m}}$
(D) $\mathrm{V}_{\mathrm{r}}>\mathrm{V}_{\mathrm{x}}<\mathrm{V}_{\mathrm{m}}$

Narayan Hari

Numerade Educator

Problem 2116

If $\lambda_{\gamma} \lambda_{\mathrm{x}}$ and $\lambda_{\mathrm{m}}$ are the wave lengths of the $\gamma$ -rays, $\mathrm{x}$ rays and micro waves respectively in space then
(A) $\lambda_{\gamma}>\lambda_{\mathrm{x}}>\lambda_{\mathrm{m}}$
(B) $\lambda_{\gamma}<\lambda_{\mathrm{x}}<\lambda_{\mathrm{m}}$
(C) $\lambda_{r}=\lambda_{x}=\lambda_{m}$
(D) $\lambda_{\gamma}<\lambda_{\mathrm{m}}<\lambda_{\mathrm{x}}$

Narayan Hari

Numerade Educator

Problem 2117

According to Maxwell, a changing electric field produces
(A) emf
(B) Electric current
(C) magnetic field
(D) radiation pressure

Narayan Hari

Numerade Educator

Problem 2118

An electromagnetic wave going through vacuum is described by $E=E_{0} \sin (k x-\cot )$. Which of the following is independent of the wavelength?
(A) $\omega$
(B) $(\mathrm{k} / \mathrm{c})$
(C) $\mathrm{k}_{\mathfrak{e}}$
(D) $\mathrm{k}$

Narayan Hari

Numerade Educator

Problem 2119

Which of the following have zero average value in a plane electromagnetic wave?
(A) Electric energy
(B) Magnetic energy
(C) Electric field
(D) None of these.

Narayan Hari

Numerade Educator

Problem 2120

If the relative permeability and dielectric constant of a given medium are equal to $\mu_{\mathrm{r}}$ and $\mathrm{K}$ respectively, then the refractive index of the medium is equal to
(A) $\sqrt{\left(\mu_{\mathrm{T}} \mathrm{K}\right)}$
(B) $\sqrt{\left(\mu_{1} E_{0}\right)}$

Narayan Hari

Numerade Educator

Problem 2121

Astronomers have found that electromagnetic waves of wavelength $21 \mathrm{~cm}$ are continuously reaching the Earth's surface. Calculate the frequency of this radiation. $\left(\mathrm{c}=3 \times 10^{8} \mathrm{~m} / \mathrm{s}\right)$
(A) $14.28 \mathrm{GHz}$
(B) $1.428 \mathrm{kHz}$
(C) $1.428 \mathrm{MHz}$
(D) $1.428 \mathrm{GHz}$

Narayan Hari

Numerade Educator

01:17

Problem 2122

Electric field in an electromagnetic wave is given by $\mathrm{E}=50 \mathrm{sin} \omega[\mathrm{t}-(\mathrm{x} / \mathrm{c})] \mathrm{N} \mathrm{C}^{-1}$. Intensity of this wave is
$\mathrm{Wm}^{-2}$
(A) 50
(B) $1.1 \times 10^{8}$
(C) $3.3$
(D) $5.5 \times 10^{-19}$

Narayan Hari

Numerade Educator

Problem 2123

The amplitude of the electric field in a parallel beam of light of intensity $2.0 \mathrm{Wm}^{-2}$ is
(A) $38.8 \mathrm{NC}^{-1}$
(B) $19.4 \mathrm{NC}^{-1}$
(C) $9.7 \mathrm{NC}^{-1}$
(D) None of these.

Narayan Hari

Numerade Educator

Problem 2124

Speed of electromagnetic wave is the same
(A) for all wavelengths
(B) in all media
(C) for all intensities
(D) for all frequencies

Narayan Hari

Numerade Educator

Problem 2125

The maximum electric field in a plane electromagnetic wave is $900 \mathrm{NC}^{-1}$. The wave is going in the $\mathrm{x}$ direction and the electric field is in the y direction. The maximum magnetic field in the wave is $\mathrm{T}$
(A) $3 \times 10^{-8}$
(B) $3 \overline{\times 10^{-6}}$ (C) $27 \times 10^{-6}$ (D) $27 \times 10^{10}$

Narayan Hari

Numerade Educator

Problem 2126

Electromagnetic waves are produced by
(A) a static charge
(B) a moving charge
(C) an accelerating charge
(D) chargeless particles

Narayan Hari

Numerade Educator

Problem 2127

Maxwells equations are derived from the laws of
(A) electricity
(B) magnetism
(C) both electricity and magnetism
(D) mechanics

Narayan Hari

Numerade Educator

Problem 2128

Which of the following electromagnetic waves has the longest wavelength?
(A) Radio waves
(B) Infrared radiations
(C) x rays
(D) visible rays

Narayan Hari

Numerade Educator

Problem 2129

Which of the following electromagnetic waves has the highest frequency?
(A) radiowaves
(B) microwaves
(C) $\gamma$ rays
(D) $\mathrm{x}$ rays

Narayan Hari

Numerade Educator

Problem 2130

Which of the following electromagnetic waves is used in telecommunication?
(A) radiowaves
(B) visible radiations
(C) ultraviolet rays
(D) microwaves

Narayan Hari

Numerade Educator

Problem 2131

The maximum value of $\mathrm{E}^{-}$ in an electromagnetic waves in air is equal to $6.0 \times 10^{-4} \mathrm{Vm}^{-1}$. The maximum value of $\mathrm{B}^{-}$ is
(A) $1.8 \times 10^{5} \mathrm{~T}$
(B) $2.0 \times 10^{4} \mathrm{~T}$
(C) $2.0 \times 10^{-12} \mathrm{~T}$
(D) $1.8 \times 10^{13} \mathrm{~T}$

Narayan Hari

Numerade Educator

Problem 2132

Dimensional formula of intensity of radiation is
(A) $\mathrm{M}^{1} \mathrm{~L}^{2} \mathrm{~T}^{-2}$
(B) $\mathrm{M}^{1} \mathrm{~L}^{0} \mathrm{~T}^{-2}$
(C) $\mathrm{M}^{1} \mathrm{~L}^{2} \mathrm{~T}^{-3}$
(D) $\overline{\mathrm{M}^{1} \mathrm{~L}^{0} \mathrm{~T}^{-3}}$

Narayan Hari

Numerade Educator

Problem 2133

The frequency of an electromagnetic wave in free space 15 $3 \mathrm{MHz}$. When it passes through a medium of relative permeability $\varepsilon_{\mathrm{r}}=4.0$, then its frequency
(A) becomes half
(B) become doubled
(C) remain same
(D) become $\sqrt{2}$ times

Narayan Hari

Numerade Educator

Problem 2134

The frequency of electromagnetic wave having wavelength $25 \mathrm{~mm}$ is $\quad \mathrm{Hz}$
(A) $1.2 \times \overline{10^{10}}$
(B) $7.5 \times 10^{5}$
(C) $1.2 \times 10^{8}$
(D) $7.5 \times 10^{6}$

Narayan Hari

Numerade Educator

Problem 2135

Unit of energy density of electromagnetic wave is
(A) $\mathrm{Jm}^{-3}$
(B) $\mathrm{Jm}^{-2}$
(C) $\mathrm{wm}^{-2}$
(D) None of these

Narayan Hari

Numerade Educator

Problem 2136

What is the ratio of velocities of light rays of wavelengths $4000^{\circ} \mathrm{A}$ and $8000^{\circ} \mathrm{A}$ in vacuum?
(A) $1: 2$
(B) $1: 1$
(C) $2: 1$
(D) cannot be determined

Narayan Hari

Numerade Educator

Problem 2137

Which of the following rays are not electromagnetic waves?
(A) $\alpha$ rays
(B) $\gamma$ rays
(C) $\beta$ rays
(D) heat rays

Narayan Hari

Numerade Educator

Problem 2138

A new system of unit is evolved in which the values of $\mu_{0}$ and $\varepsilon_{0}$ are 2 and 8 respectively. Then the speed of light in this system will be
(A) $0.25$
(B) $0.5$
(C) $0.75$
(D) 1

Narayan Hari

Numerade Educator

Problem 2139

Our eyes respond to wavelength ranging from
(A) $400 \mathrm{~nm}$ to $700 \mathrm{~nm}$
(B) $-\infty$ to $+\infty$
(C) $1 \mathrm{~mm}$ to $700 \mathrm{~nm}$
(D) $700 \mathrm{~nm}$ to $800 \mathrm{~nm}$

Narayan Hari

Numerade Educator

Problem 2140

In microwave oven, we use electromagnetic oscillators which produce electromagnetic waves in the wavelength range
(A) $1 \mathrm{~mm}$ to $10 \mathrm{~m}$
(B) $0.7 \mu \mathrm{m}$ to $1 \mathrm{~mm}$
(C) $0.1 \mathrm{~m}$ to $1 \mathrm{~mm}$
(D) $0.1 \mu \mathrm{m}$ to $0.7 \mu \mathrm{m}$

Narayan Hari

Numerade Educator

Problem 2141

What is the direction of $\mathrm{E}^{-} \times \mathrm{B}^{-}$ in an electromagnetic wave?
(A) same as that of $E^{-}$
(B) same as that of $\mathrm{B}^{-}$
(C) same as the direction of propagation of electromagnetic wave
(D) none of these

Narayan Hari

Numerade Educator

Problem 2142

The wavelength of $\mathrm{x}$ rays is of the order of
(A) $1 \mathrm{~cm}$
(B) $1 \mathrm{~m}$
(C) Imicron
(D) 1angstrom

Narayan Hari

Numerade Educator

02:16

Problem 2143

A plane electromagnetic wave of frequency $25 \mathrm{MHz}$ travels in free space along the $\mathrm{x}$ direction. At a particular point in space and time $\mathrm{E}^{-}=6.3 \mathrm{j} \wedge \mathrm{Vm}^{-1}$ then $\mathrm{B}^{-}$ at this point is
(A) $2.1 \times 10^{-8}$ i $\mathrm{T}$
(B) $2.1 \times 10^{-8} \mathrm{k} \wedge \mathrm{T}$
(C) $1.89 \times 10^{9} \mathrm{k} \wedge \mathrm{T}$
(D) $2.52 \times 10^{-7} \mathrm{k} \wedge \mathrm{T}$

Ankur Khosla

Numerade Educator

01:30

Problem 2144

Ankur Khosla

Numerade Educator

02:30

Problem 2145

Light with an energy flux of $18 \mathrm{w} / \mathrm{m}^{2}$ or $\mathrm{Wm}^{-2}$ falls on a non-reflecting surface at normal to surface. If the surface has an area of $20 \mathrm{~m}^{2}$. The average force exerted on the surface during 30 minutes is
(A) $6.48 \times 10^{5} \mathrm{~N}$
(B) $3.60 \times 10^{2} \mathrm{~N}$
(C) $1.2 \times 10^{-6} \mathrm{~N}$
(D) $2.16 \times 10^{-3} \mathrm{~N}$

Khoobchandra Agrawal

Numerade Educator

Problem 2146

Energy density of an electromagnetic wave of intensity $0.02 \mathrm{Wm}^{-2}$ is
(A) $6.67 \times 10^{-11} \mathrm{Jm}^{-3}$
(B) $6 \times 10^{6} \mathrm{Jm}^{-3}$
(C) $1.5 \times 10^{10} \mathrm{Jm}^{-3}$
(D) none of the above

Narayan Hari

Numerade Educator

Problem 2147

The waves used in communication are generally called
(A) $\gamma$ rays
(B) $\alpha$ rays
(C) microwaves
(D) radiowaves

Narayan Hari

Numerade Educator

01:10

Problem 2148

For an electromagnetic wave, the phase difference between
vectors $\mathrm{E}^{-}$ and $\mathrm{B}^{-}$ (far away from the source)
(A) 0
(B) $[\pi / 2]$
(C) $\pi$
(D) $[3 \pi / 2]$

Ankur Khosla

Numerade Educator

Problem 2149

In an electromagnetic wave, if the amplitude of magnetic field is $3 \times 10^{-10} \mathrm{~T}$, the amplitude of the associated electric field will be
(A) $9 \times 10^{-2} \overline{\mathrm{Vm}^{-1}}$
(B) $3 \times 10^{-10} \mathrm{Vm}^{-1}$
(C) $3 \times 10^{-2} \mathrm{Vm}^{-1}$
(D) $1 \times 10^{-18} \mathrm{Vm}^{-1}$

Narayan Hari

Numerade Educator

Problem 2150

The electric and magnetic field of an electromagnetic wave are
(A) in phase and perpendicular to each other
(B) in phase and parallel to each other
(C) in opposite phase and perpendicular to each other
(D) in opposite phase and parallel to each other

Narayan Hari

Numerade Educator

01:10

Problem 2151

The direction of electric and magnetic vector tor an electromagnetic wave travelling along X-axis are shown in fig. $A$ and $B$ then(A) A is correct, B is wrong
(B) B is correct, $\mathrm{A}$ is wrong
(C) Both $\mathrm{A}$ and $\mathrm{B}$ are correct
(D) Both $\mathrm{A}$ and $\mathrm{B}$ are wrong

Narayan Hari

Numerade Educator

Problem 2152

The dimensions of $(1 / \mu \varepsilon)$ are
(A) $\mathrm{M}^{0} \mathrm{~L}^{1} \mathrm{~T}^{-1}$
(B) $\mathrm{M}^{0} \mathrm{~L}^{-1} \mathrm{~T}^{1}$
(C) $\mathrm{M}^{0} \mathrm{~L}^{2} \mathrm{~T}^{-2}$
(D) $\mathrm{M}^{0} \mathrm{~L}^{1} \mathrm{~T}^{-2}$

Narayan Hari

Numerade Educator

Problem 2153

(A) $\mathrm{M}^{0} \mathrm{~L}^{-1} \mathrm{~T}^{-1}$
(B) $\mathrm{M}^{0} \mathrm{~L}^{1} \mathrm{~T}^{-1}$
(C) $\mathrm{M}^{0} \mathrm{~L}^{2} \mathrm{~T}^{-2}$
(D) $\mathrm{M}^{0} \mathrm{~L}^{0} \mathrm{~T}^{0}$

Narayan Hari

Numerade Educator

Problem 2154

The frequency of light wave of wavelength $5000 \mathrm{~A}$ is $\mathrm{Hz}$
(A) $6 \times 10^{14}$
(B) $1.5 \times 10^{-2}$
(C) $1.5$
(D) $6 \times 10^{1}$

Narayan Hari

Numerade Educator

Problem 2155

Unit of $\mu_{0} \mathrm{C}$ is same as that of
(A) current
(B) resistance
(C) electric charge
(D) velocity

Narayan Hari

Numerade Educator

Problem 2156

The amplitude of the magnetic field part of an electromagnetic wave in vacuum is $\mathrm{Bm}=510 \mathrm{nT}$. Then the amplitude of the electric part of the wave is
(A) $1.53 \times 10^{11} \mathrm{~V} / \mathrm{m}$
(B) $1.53 \mathrm{~V} / \mathrm{m}$
(C) $1.53 \times 10^{2} \mathrm{~V} / \mathrm{m}$
(D) $1.53 \times 10^{8} \mathrm{~V} / \mathrm{m}$

Narayan Hari

Numerade Educator

02:33

Problem 2157

If the direction of magnetic field $\mathrm{B}^{\rightarrow}$ at some instant is along + ve $Z$ direction and the electromagnetic wave is propagating along + ve $\mathrm{X}$ direction, then the direction of electric field $\mathrm{E}^{\rightarrow}$ at that instant is
(A) along - ve Y direction
(B) along + ve Y direction
(C) along + ve $\mathrm{X}$ direction
(B) along - ve $\mathrm{X}$ direction

Ankur Khosla

Numerade Educator

01:08

Problem 2158

Relation between amplitudes of electric and Magnetic field is
(A) $E_{0}=B_{0}$
(B) $E_{0}=\mathrm{cB}_{0}$
(C) $E_{0}=\left(B_{0} / c\right)$
(D) $E_{0}=\left(\mathrm{c} / \mathrm{B}_{0}\right)$

Ankur Khosla

Numerade Educator

01:23

Problem 2159

If a source is transmitting electromagnetic wave of frequency $8.2 \times 10^{6} \mathrm{~Hz}$, then the wavelength of the electromagnetic waves transmitted from the source will be
(A) $36.6 \mathrm{~m}$
(B) $42.3 \mathrm{~m}$
(C) $40.5 \mathrm{~m}$
(D) $50.9 \mathrm{~m}$

Ankur Khosla

Numerade Educator

01:37

Problem 2160

The velocity of light in vacuum can be changed by changing
(A) frequency
(B) wavelength
(C) amplitude
(D) none of these

Ankur Khosla

Numerade Educator

01:34

Problem 2161

An electromagnetic wave going through vacuum is described by $E=E_{0} \sin (k x-\omega t)$ then $B=B_{0} \sin (k x-\omega t)$ then
(A) $E_{0} B_{0}=\operatorname{cok}$
(B) $E_{0} k=B_{0} \omega$
(C) $\mathrm{E}_{0} \mathrm{~m}=\mathrm{B}_{0} \mathrm{k}$
(D) none of these

Ankur Khosla

Numerade Educator

01:48

Problem 2162

If the wavelength of light is $4000^{\circ} \mathrm{A}$ then the number of waves in $1 \mathrm{~mm}$ length will be
(A) $2.5$
(B) 2500
(C) 250
(D) 25000

Ankur Khosla

Numerade Educator

01:17

Problem 2163

The SI unit of displacement current is
(A) coulomb
(B) henry
(C) ampere
(D) faraday

Ankur Khosla

Numerade Educator

Problem 2164

The electromagnetic waves do not transport
(A) energy
(B) charge
(C) momentum
(D) information

Ajay Singhal

Numerade Educator

01:43

Problem 2165

An electric charge oscillating with a frequency of 1 kilo cycles/s can radiates electromagnetic waves of wavelength
(A) $100 \mathrm{~km}$
(B) $200 \mathrm{~km}$
(C) $300 \mathrm{~km}$
(D) $400 \mathrm{~km}$

Ankur Khosla

Numerade Educator

01:43

Problem 2166

The frequency $1057 \mathrm{MHz}$ of radiation arising from two close energy levels in hydrogen belongs to
(A) radio waves
(B) infrared waves
(C) micro waves
(D) \gamma rays

Ankur Khosla

Numerade Educator

01:58

Problem 2167

Electromagnetic waves travelling in a medium which has relative permeability $1.3$ and relative permittivity $2.14$ speed of electromagnetic waves in this medium will be
(A) $3.6 \times 10^{8} \mathrm{~m} / \mathrm{s}$
(B) $1.8 \times 10^{8} \mathrm{~m} / \mathrm{s}$
(C) $1.8 \times 10^{6} \mathrm{~m} / \mathrm{s}$
(D) $13.6 \times 10^{6} \mathrm{~m} / \mathrm{s}$

Ankur Khosla

Numerade Educator

01:19

Problem 2168

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) $p \neq 0, E \neq 0$
(C) $p \neq 0, E=0$
(D) $p=0, E \neq 0$

Ajay Singhal

Numerade Educator

01:19

Problem 2169

Maxwell's modified form of Ampere's circuital law is
(A) $\oint \mathrm{B}^{-} \cdot \mathrm{dS}^{-}$
(B) $\phi \mathrm{B}^{-} \cdot \mathrm{dS}^{-}=\mu_{\mathrm{o}} \mathrm{i}$
(C) $\oint \mathrm{B}^{-} \cdot \mathrm{d} \ell^{-}=\mu_{\mathrm{o}} \mathrm{i}+\mu_{0} \in_{0}\left(\mathrm{~d} \Phi_{\mathrm{E}} / \mathrm{dt}\right)$
(D) $\oint \mathrm{B}^{-} \cdot \mathrm{d} \mathcal{\ell}^{-}=\mu_{0} \mathrm{i}+\left(1 / \in_{0}\right)\left(\mathrm{d}_{\mathrm{q}} / \mathrm{dt}\right)$

Ankur Khosla

Numerade Educator

01:14

Problem 2170

The wavelength of $\mathrm{x}$ rays is of the order of
(A) $10^{-3} \mathrm{~m}$
(B) $10^{-5} \mathrm{~m}$
(C) $10^{-10} \mathrm{~m}$
(D) $10^{-12} \mathrm{~m}$

Ankur Khosla

Numerade Educator

03:07

Problem 2171

A point source of electromagnetic radiation has an average output power of $800 \mathrm{~W}$. The maximum value of electric field at a distance of $4.0 \mathrm{~m}$ from the source is
(A) $64.7 \mathrm{Vm}^{-1}$
(B) $57.8 \mathrm{Vm}^{-1}$
(C) $56.72 \mathrm{Vm}^{-1}$
(D) $54.77 \mathrm{Vm}^{-1}$

Ankur Khosla

Numerade Educator

01:18

Problem 2172

A plane electromagnetic wave $E_{z}=100 \cos \left(6 \times 10^{8} t+4 x\right) \operatorname{Vm}^{-1}$ propagate in a medium of
refractive index
(A) $1.5$
(B) $2.0$
(C) $2.4$
(D) $4.0$

Ankur Khosla

Numerade Educator

Problem 2173

A plane electromagnetic wave of wave intensity $10 \mathrm{~cm}^{-2}$ strikes a small mirror of area $20 \mathrm{~cm}^{2}$, held perpendicular to the approaching wave. The radiation force on the mirror will be
(A) $6.6 \times 10^{-11} \mathrm{~N}$
(B) $1.33 \times 10^{-11} \mathrm{~N}$
(C) $1.33 \times 10^{-10} \mathrm{~N}$
(D) $6.6 \times 10^{-10} \mathrm{~N}$

Khoobchandra Agrawal

Numerade Educator

02:12

Problem 2174

An observer is at $2 \mathrm{~m}$ from an isotropic point source of light emitting $40 \mathrm{w}$ power. The rm.s value of electric due to the source at the position of the observer is
(A) $5.77 \times 10^{-8} \mathrm{Vm}^{-1}$
(B) $17.3 \mathrm{Vm}^{-1}$
(C) $57.7 \times 10^{-8} \mathrm{Vm}^{-1}$
(D) $1.73 \mathrm{Vm}^{-1}$

Ankur Khosla

Numerade Educator

01:07

Problem 2175

Electromagnetic waves used in medicine to destroy cancer cells
(A) radio waves
(B) infrared rays
(C) gamma rays
(D) ultraviolet rays

Ankur Khosla

Numerade Educator

01:49

Problem 2176

What is the name associated with the equation
$E^{\longrightarrow} \cdot d t^{-}=-(d \Phi \beta / d t)$
(A) Gauss law for electricity
(B) Gauss law for magnetism
(C) ampere's law
(D) faraday's law

Ankur Khosla

Numerade Educator

01:10

Problem 2177

What oscillates in an electromagnetic wave?
(A) $\mathrm{E}^{-}$ and $\mathrm{B}^{-}$
(B) $\mathrm{B}^{-}$
(C) $E^{-}$
(D) none of these

Ankur Khosla

Numerade Educator

Problem 2178

Which of the following rays are not electromagnetic waves?
(A) a rays
(B) rrays
(C) $\beta$ rays
(D) heat rays

Ankur Khosla

Numerade Educator

02:02

Problem 2179

The rms value of the electric field of the light coming from the sun is $720 \mathrm{~N} / \mathrm{c}$. The average total energy density of the electromagnetic wave is
(A) $4.58 \times 10^{-6} \mathrm{Jm}^{-3}$
(B) $6.3 \times 10^{-9} \mathrm{Jm}^{-3}$
(C) $81.35 \times 10^{-12} \mathrm{Jm}^{-3}$
(D) $3.3 \times 10^{-3} \mathrm{Jm}^{-3}$

Ankur Khosla

Numerade Educator

Problem 2180

What is the wave length of range of electromagnetic waves?
(A) $10^{-8} \mathrm{~m}$ to $10^{15} \mathrm{~m}$
(B) $10^{-15} \mathrm{~m}$ to $10^{8} \mathrm{~m}$
(C) $10^{-15} \mathrm{~m}$ to $10^{15} \mathrm{~m}$
(D) $10^{8} \mathrm{~m}$ to $10^{15} \mathrm{~m}$

Ankur Khosla

Numerade Educator

01:22

Problem 2181

What is the wavelength range of visible light?
(A) $10 \mathrm{~A}$ to $100 \mathrm{~A}$
(B) $4000 \mathrm{~A}$ to $7000 \mathrm{~A}$
(C) $8000 \AA$ to $10000 \AA$
(D) $10000 \AA$ to $15000 \AA$

Ankur Khosla

Numerade Educator

01:25

Problem 2182

Unit of $\mu_{0} \mathrm{c}$ is same as that of
(A) current
(B) resistance
(C) electric charge
(D) velocity

Ankur Khosla

Numerade Educator

01:06

Problem 2183

In electromagnetic spectrum, the visible light lie between
(A) radiowaves and microwaves
(B) ultraviolet rays and infrared rays
(C) ultraviolet rays and $\mathrm{x}$ rays
(D) infrared rays and microwaves

Ankur Khosla

Numerade Educator

Problem 2184

Which of the following statements is not true in case of electromagnetic waves?
(A) they are light waves
(B) they are transverse waves
(C) propagates through space
(D) they are longitudinal waves

Ankur Khosla

Numerade Educator

01:09

Problem 2185

The oscillating electric and magnetic field vectors of an electromagnetic waves far away from source are oriented along
(A) Mutually perpendicular direction and differ in phase by $90^{\circ}$
(B) Mutually perpendicular and in same phase
(C) In same direction and in same phase
(D) In same direction and differ in phase by $90^{\circ}$

Ankur Khosla

Numerade Educator

02:05

Problem 2186

Which of the following option of electromagnetic waves is in order of increasing frequency ?
(A) microwaves, ultraviolet rays, $\mathrm{x}$ rays
(B) gamma rays, ultraviolet rays, radiowaves
(C) radiowaves, visible light, infrared rays
(D) gamma rays, visible light, ultraviolet rays

Ankur Khosla

Numerade Educator

01:13

Problem 2187

The sun delivers $10^{3} \mathrm{Wm}^{-2}$ of electromagnetic flux to earth's surface. The total power that is incident on a roof of dimension $8 \mathrm{~m} \times 20 \mathrm{~m}$ will be
(A) $4 \times 10^{5} \mathrm{w}$
(B) $2.56 \times 10^{4} \mathrm{w}$
(C) $6.4 \times 10^{5} \mathrm{w}$
(D) $1.6 \times 10^{5} \mathrm{w}$

Ankur Khosla

Numerade Educator

01:07

Problem 2188

Bolometer is used to detect
(A) infrared rays
(B) ultraviolet rays
(C) x rays
(D) $\gamma$ rays

Ankur Khosla

Numerade Educator

01:13

Problem 2189

Range of frequency of microwaves is about
(A) $530 \mathrm{kHz}$ to $1710 \mathrm{kHz}$
(B) $54 \mathrm{MHz}$ to $890 \mathrm{MHz}$
(C) $3 \mathrm{GHz}$ to $300 \mathrm{GHz}$
(D) $4 \times 10^{14} \mathrm{~Hz}$ to $7 \times 10^{14} \mathrm{~Hz}$

Ankur Khosla

Numerade Educator

01:07

Problem 2190

SI unit of displacement current is
(A) coulomb
(B) ampere
(C) faraday
(D) volt

Ankur Khosla

Numerade Educator

02:01

Problem 2191

The frequencies of $\mathrm{x}$ rays, $\gamma$ rays and ultraviolet rays are respectively $\mathrm{p}, \mathrm{q}$ and $\mathrm{r}$ then
(A) $p<q, q>r$
(B) $p>q, q>r$
(C) $p>q, q<r$
(D) $p<q, q<r$

Ankur Khosla

Numerade Educator

01:38

Problem 2192

At room temperature, if the relative permittivity of water is 80 and the relative permeability be $0.0222$ then the velocity of light in water is $\mathrm{m} / \mathrm{s}$
(A) $2.5 \times 10^{8}$
(B) $2.26 \times 10^{8}$
(C) $3.5 \times 10^{8}$
(D) $3 \times 10^{8}$

Ankur Khosla

Numerade Educator

01:30

Problem 2193

If the electric field associated with a radiation of frequency $10 \mathrm{MH} z$ is $\mathrm{E}=10 \sin (\mathrm{kx}-\omega \mathrm{t}) \mathrm{mV} / \mathrm{m}$ then its energy density is
$\mathrm{Jm}^{-3}\left(\varepsilon_{0}=8.85 \times 10^{-12} \mathrm{C}^{2} \mathrm{~N}^{-1} \mathrm{~m}^{-2}\right)$
(A) $4.425 \times 10^{-10}$
(B) $6.26 \times 10^{-14}$
(C) $8.85 \times 10^{-16}$
(D) $8.85 \times 10^{-14}$

Ankur Khosla

Numerade Educator

02:26

Problem 2194

In an electromagnetic wave in free space, the direction of
electric field vector $E^{-}$ is along $y$ axis and magnetic field
vector $\mathrm{B}^{-}$ is along $\mathrm{z}$ axis then which of the following is true
(A) $\left(\mathrm{E}^{-} \times \mathrm{B}^{-}\right) \times \mathrm{E}^{-}=1$
(B) $\left(\mathrm{E}^{-} \times \mathrm{B}^{-}\right) \times \mathrm{B}^{-}=1$
(C) $\left(\mathrm{E}^{-} \times \mathrm{B}^{-}\right) \times \mathrm{B}^{-}=0$
(D) none of these

Ankur Khosla

Numerade Educator

01:06

Problem 2195

When a plane electromagnetic wave travels in vacuum, the average electric energy density is given by $\left(E_{0}\right.$ is the amplitude of the electric field)
(A) $(1 / 4) \varepsilon_{0} E_{0}^{2}$
(B) $(1 / 2) \varepsilon_{0} E_{0}^{2}$
(C) $2 e_{\mathrm{o}} \mathrm{E}_{\mathrm{O}}^{2}$
(D) $4 \varepsilon_{0} E_{0}^{2}$

Ankur Khosla

Numerade Educator

02:26

Problem 2196

In a plane electromagnetic wave, the electric field oscillates sinusoidaly at a frequency of $2.0 \times 10^{10} \mathrm{~Hz}$. if the peak value of electric field is $60 \mathrm{Vm}^{-1}$ the average energy density (in $\mathrm{Jm}^{-3}$ ) of the magnetic field of the wave will be (given $\left.\mu_{0}=4 \pi \times 10^{-7} \mathrm{Tm} / \mathrm{A}\right)$
(A) $2 \pi \times 10^{-7}$
(B) $(1 / 2 \pi) \times 10^{-7}$
(C) $4 \pi \times 10^{-7}$
(D) $(1 / 4 \pi) \times 10^{-7}$

Ankur Khosla

Numerade Educator

01:39

Problem 2197

Which of the following pairs of the component of space and time varying $\mathrm{E}^{-}=\left(\mathrm{E}_{\mathrm{x}} \mathrm{i} \wedge+\mathrm{Eyj} \wedge+\mathrm{Ezk} \wedge\right)$ and
$\mathrm{B}^{-}=\left(\mathrm{B}_{\mathrm{x}} \mathrm{i}^{\mathrm{i}}+\mathrm{Byj}^{\wedge}+\mathrm{Bzk} \wedge\right)$ would generate a plane
electromagnetic wave travelling in $+$ ve $z$ direction
(A) $E x, B y$
(B) $\mathrm{Ey}, \mathrm{Bz}$
(C) $\mathrm{Ex}, \mathrm{Bz}$
(D) $E z, B x$

Ankur Khosla

Numerade Educator

Problem 2198

Infrared radiations are detected by
(A) spectrometer
(B) bolometer
(C) photocells
(D) geiger tubes

Ankur Khosla

Numerade Educator

01:11

Problem 2199

Electromagnetic wave is produced by oscillating electric and
magnetic fields $E^{-}$ and $B^{-}$. Choose only the incorrect statement from the following
(A) $\mathrm{E}^{-}$ is perpendicular to $\mathrm{B}^{-}$.
(B) $E^{-}$ is perpendicular to the direction of propagation of the wave
(C) $\mathrm{B}^{-}$ is perpendicular to the direction of propagation of the wave
(D) $E^{-}$ is parallel to $\mathrm{B}^{-}$

Ankur Khosla

Numerade Educator

01:35

Problem 2200

The potential difference between the plates of a parallel plate capacitor is charging at the rate of $10^{6} \mathrm{Vs}^{-1}$. If the capatance is $2 \mu \mathrm{F}$. The displacement current in the dielectric of the capacitor will be
(A) $4 \mathrm{~A}$
(B) $3 \mathrm{~A}$
(C) $2 \mathrm{~A}$
(D) $1 \mathrm{~A}$

Ankur Khosla

Numerade Educator

01:15

Problem 2201

Which of the following electromagnetic wave has the least frequency?
(A) radiowave
(B) infrared radiation
(C) microwave
(D) x rays

Ankur Khosla

Numerade Educator

00:55

Problem 2202

Which of the following electromagnetic wave has the least wavelength?
(A) radiowave
(B) visible wave
(C) ultraviolet rays
(D) microwaves

Ankur Khosla

Numerade Educator

01:26

Problem 2203

Which of the following waves are not transverse in nature?
(A) light emitted from a sodium lamp
(B) sound waves travelling in air
(C) $\mathrm{x}$ rays from an $\mathrm{x}$ ray machine
(D) microwaves used in radar

Ankur Khosla

Numerade Educator

01:06

Problem 2204

An electromagnetic wave
(A) can be deflected by electric field
(B) can be deflected by magnetic field
(C) can be deflected by both electric and magnetic field
(D) none of these

Ankur Khosla

Numerade Educator

01:25

Problem 2205

When an electromagnetic wave encounters a dielectric medium, the transmitted wave has
(A) same frequency but different amplitude
(B) same amplitude but different frequency
(C) same frequency and amplitude
(D) different frequency and amplitude

Ankur Khosla

Numerade Educator

01:13

Problem 2206

According to Maxwell, a changing electric field produces
(A) emf
(B) radiation pressure
(C) electric current
(D) magnetic field

Ankur Khosla

Numerade Educator

00:52

Problem 2207

was the first to predict the existence of electromagnetic waves.
(A) Maxwell
(B) Faraday
(C) Ampere
(D) hertz

Ankur Khosla

Numerade Educator