NEET > Electromagnetic Waves

Explore popular questions from Electromagnetic Waves for NEET. This collection covers Electromagnetic Waves previous year NEET questions hand picked by popular teachers.


Q 1.    

Correct4

Incorrect-1

An electromagnetic wave in vacuum has the electric and magnetic field {tex} \vec { E } {/tex} and {tex} \vec { B } {/tex} , which are always perpendicular to each other. The direction of polarization is given by {tex} \vec { X } {/tex} and that of wave propagation by {tex} \vec { k } . {/tex} Then

A

{tex} \overline { X } \| \vec { B } {/tex} and {tex} \vec { k } \| \vec { B } \times \vec { E } {/tex}

{tex} \overline { X } \| \overline { E } {/tex} and {tex} \vec { k } \| \vec { E } \times \vec { B } {/tex}

C

{tex} \vec { X } \| \vec { B } {/tex} and {tex} \vec { k } \| \vec { E } \times \vec { B } {/tex}

D

{tex} \vec { X } \| \vec { E } {/tex} and {tex} \vec { k } \| \vec { B } \times \vec { E } {/tex}

Explanation

Q 2.    

Correct4

Incorrect-1

The rms value of the electric field of the light coming from the Sun is 720 {tex} \mathrm { N } / \mathrm { C } {/tex} . The average total energy density of the electromagnetic wave is

{tex} 4.58 \times 10 ^ { - 6 } \mathrm { J } / \mathrm { m } ^ { 3 } {/tex}

B

{tex} 6.37 \times 10 ^ { - 9 } \mathrm { J } / \mathrm { m } ^ { 3 } {/tex}

C

{tex} 81.35 \times 10 ^ { - 12 } \mathrm { J } / \mathrm { m } ^ { 3 } {/tex}

D

{tex} 3.3 \times 10 ^ { - 3 } \mathrm { J } / \mathrm { m } ^ { 3 } {/tex}

Explanation

Q 3.    

Correct4

Incorrect-1

In order to establish an instantancous displacemet current of 1{tex} \mathrm { mA } {/tex} in the space between the plates of 2{tex} \mu \mathrm { F } {/tex} parallel plate capacitor, the potential difference need to apply is

A

100 {tex} \mathrm { Vs } ^ { - 1 } {/tex}

B

200 {tex} \mathrm { Vs } ^ { - 1 } {/tex}

C

300 {tex} \mathrm { Vs } ^ { - 1 } {/tex}

500 {tex} \mathrm { Vs } ^ { - 1 } {/tex}

Explanation

Q 4.    

Correct4

Incorrect-1

During the propagation of electromagnetic waves in a medium:

A

Electric energy density is double of the magnetic energy density.

B

Electric energy density is half of the magnetic energy density.

Electric energy density is equal to the magnetic energy density.

D

Both electric and magnetic energy densities are zero.

Explanation

Q 5.    

Correct4

Incorrect-1

An electromagnetic wave with frequency {tex} \omega {/tex} and wavelength {tex} \lambda {/tex} travels in the {tex} + y {/tex} direction. Its magnetic field is along {tex} + x - {/tex}axis. The vector equation for the associated electric field (of {tex} \left. \text { amplitude } E _ { 0 } \right) {/tex} is

A

{tex} \vec { E } = - E _ { 0 } \cos \left( \omega t + \frac { 2 \pi } { \lambda } y \right) \hat { x } {/tex}

B

{tex} \vec { E } = E _ { 0 } \cos \left( \omega t - \frac { 2 \pi } { \lambda } y \right) \hat { x } {/tex}

{tex} \vec { E } = E _ { 0 } \cos \left( \omega t - \frac { 2 \pi } { \lambda } y \right) \hat { z } {/tex}

D

{tex} \vec { E } = - E _ { 0 } \cos \left( \omega t + \frac { 2 \pi } { \lambda } y \right) \hat { z } {/tex}

Explanation

Q 6.    

Correct4

Incorrect-1

An electromagnetic wave of frequency {tex} v = 3.0 \mathrm { MHz } {/tex} passes from vacuum into a dielectric medium with permittivity {tex} \mathrm { E } = 4.0 . {/tex} Then

wavelength is halved and frequency remains unchanged

B

wavelength is doubled and frequency becomes half

C

wavelength is doubled and the frequency remains unchanged

D

wavelength and frequency both remain unchanged.

Explanation

Q 7.    

Correct4

Incorrect-1

The average electric field of electromagnetic waves in certain region of free space is {tex} 9 \times 10 ^ { - 4 } \mathrm { NC } ^ { - 1 } {/tex} . Then the average magnetic field in the same region is of the order of

A

{tex} 27 \times 10 ^ { - 4 } \mathrm { T } {/tex}

{tex} 3 \times 10 ^ { - 12 } \mathrm { T } {/tex}

C

{tex} \left( \frac { 1 } { 3 } \right) \times 10 ^ { - 12 } \mathrm { T } {/tex}

D

{tex} 3 \times 10 ^ { 12 } \mathrm { T } {/tex}

Explanation

Q 8.    

Correct4

Incorrect-1

The electric field of an electromagnetic wave travelling through vaccum is given by the equation {tex} E = E _ { 0 } \sin ( k x - \omega t ) . {/tex} The quantity that is independent of wavelength is

A

{tex} k \omega {/tex}

{tex} \frac { k } { \omega } {/tex}

C

{tex} k ^ { 2 } \omega {/tex}

D

{tex}\omega{/tex}

Explanation

Q 9.    

Correct4

Incorrect-1

The electric and the magnetic field associated with an E.M. wave, propagating along the {tex} + z {/tex} -axis, can be represented by

{tex} \left[ \overrightarrow { \mathrm { E } } = \mathrm { E } _ { 0 } \hat { \mathrm { i } } , \overrightarrow { \mathrm { B } } = \mathrm { B } _ { 0 } \hat { \mathrm { j } } \right] {/tex}

B

{tex} \left[ \overrightarrow { \mathrm { E } } = \mathrm { E } _ { 0 } \overrightarrow { \mathrm { k } } , \overrightarrow { \mathrm { B } } = \mathrm { B } _ { 0 } \hat { \mathrm { i } } \right] {/tex}

C

{tex} \left[ \overrightarrow { \mathrm { E } } = \mathrm { E } _ { 0 } \hat { \mathrm { j } } , \overrightarrow { \mathrm { B } } = \mathrm { B } _ { 0 } \hat { \mathrm { i } } \right] {/tex}

D

{tex} \left[ \overrightarrow { \mathrm { E } } = \mathrm { E } _ { 0 } \hat { \mathrm { j } } , \overrightarrow { \mathrm { B } } = \mathrm { B } _ { 0 } \hat { \mathrm { k } } \right] {/tex}

Explanation

Q 10.    

Correct4

Incorrect-1

The energy of electromagnetic wave in vacuum is given by the relation

A

{tex} \frac { E ^ { 2 } } { 2 \varepsilon _ { 0 } } + \frac { B ^ { 2 } } { 2 \mu _ { 0 } } {/tex}

B

{tex} \frac { 1 } { 2 } \varepsilon _ { 0 } \mathrm { E } ^ { 2 } + \frac { 1 } { 2 } \mu _ { 0 } \mathrm { B } ^ { 2 } {/tex}

C

{tex} \frac { E ^ { 2 } + B ^ { 2 } } { c } {/tex}

{tex} \frac { 1 } { 2 } \varepsilon _ { 0 } \mathrm { E } ^ { 2 } + \frac { \mathrm { B } ^ { 2 } } { 2 \mu _ { 0 } } {/tex}

Explanation

Q 11.    

Correct4

Incorrect-1

A plane electromally and is perfectly reflected. If energy {tex} \mathrm { E } {/tex} of area {tex} \mathrm { A } {/tex} , normally and is perfectly reflected. If energy {tex} \mathrm { E } {/tex} strikes the surface in time {tex} \mathrm { t } {/tex} then average pressure exerted on the surface is {tex} ( \mathrm { c } = \text { speed of light) } {/tex}

A

zero

B

E/Atc

{tex}2 \mathrm { E } / \mathrm { Atc } {/tex}

D

{tex} \mathrm { E } / \mathrm { c } {/tex}

Explanation

Q 12.    

Correct4

Incorrect-1

An electromagnetic wave travels along {tex} \mathrm { z } {/tex} -axis. Which of the following pairs of space and time varying fields would generate such a wave?

{tex} \mathrm { E } _ { \mathrm { x } } , \mathrm { B } _ { \mathrm { y } } {/tex}

B

{tex} E _ { y } , B _ { x } {/tex}

C

{tex} \mathrm { E } _ { Z } , \mathrm { B } _ { \mathrm { X } } {/tex}

D

{tex} E _ { y } , B _ { z } {/tex}

Explanation

Q 13.    

Correct4

Incorrect-1

The magnetic field in a travelling electromagnetic wave has a peak value of 20{tex} \mathrm { nT } {/tex} . The peak value of electric field strength

A

{tex}3 \mathrm { V } / \mathrm { m } {/tex}

{tex}6 \mathrm { V } / \mathrm { m } {/tex}

C

{tex}9 \mathrm { V } / \mathrm { m } {/tex}

D

{tex}12 \mathrm { V } / \mathrm { m } {/tex}

Explanation

Q 14.    

Correct4

Incorrect-1

Microwave oven acts on the principle of:

A

giving rotational energy to water molecules

B

giving translational energy to water molecules

giving vibrational energy to water molecules

D

transferring electrons from lower to higher energy levels in water molecule

Explanation

Q 15.    

Correct4

Incorrect-1

Displacement current is

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

Explanation

Q 16.    

Correct4

Incorrect-1

The electric field associated with an e.m. wave in vacuum is given by {tex} \vec { E } = \hat { i } 40 \cos \left( k z - 6 \times 10 ^ { 8 } t \right) , {/tex} where {tex} E , z {/tex} and {tex} t {/tex} are in volt/m {tex} , {/tex} meter and seconds respectively. The value of wave vector {tex} k {/tex} is

2{tex} m ^ { - 1 } {/tex}

B

0.5{tex} \mathrm { m } ^ { - 1 } {/tex}

C

6{tex} m ^ { - 1 } {/tex}

D

3{tex} m ^ { - 1 } {/tex}

Explanation

Q 17.    

Correct4

Incorrect-1

The charge on a parallel plate capacitor varies as {tex} q = q _ { 0 } {/tex} cos {tex} 2 \pi u t . {/tex} The plates are very large and close together {tex} \text { (area } = A , \text { separation } = d ) . {/tex} The displacement current through the capacitor is

A

{tex} q _ { 0 } 2 \pi {v} \sin \pi { v } t {/tex}

{tex} - q _ { 0 } 2 \pi { v } \sin 2 \pi { v } t {/tex}

C

{tex} q _ { 0 } 2 \pi \sin \pi { v } t {/tex}

D

{tex} q _ { 0 } \pi v \sin 2 \pi v t {/tex}

Explanation

Q 18.    

Correct4

Incorrect-1

A radiation of energy {tex} \mathrm { 'E' } {/tex} falls normally on a perfectly reflecting surface. The momentum transferred to the surface is {tex} ( \mathrm { C } = \text { Velocity of light) } {/tex}

{tex} \frac { 2 \mathrm { E } } { \mathrm { C } } {/tex}

B

{tex} \frac { 2 \mathrm { E } } { \mathrm { C } ^ { 2 } } {/tex}

C

{tex} \frac { E } { C ^ { 2 } } {/tex}

D

{tex} \frac { E } { C } {/tex}

Explanation

Q 19.    

Correct4

Incorrect-1

Match List-I (Electromagnetic wave type) with List-II (Its association/application) and select the correct option from the choices given below the lists:

A

(iv) (iii) (ii) (i)

B

(i) (ii) (iv) (iii)

C

(iii) (ii) (i) (iv)

(i) (ii) (iii) (iv)

Explanation

Q 20.    

Correct4

Incorrect-1

A plane electromagnetic wave travels in free space alongX-direction. If the value of B(in tesla) at a particular pointin space and time is {tex}1.2 \times 10^{–8}{/tex} k. The value of {tex}\overrightarrow{E}{/tex} (in {tex}Vm^{–1}{/tex}) at that point is

A

1.2{tex} \hat { \mathrm { j } } {/tex}

B

3.6{tex} \mathrm { \hat{k} } {/tex}

C

1.2{tex} \hat { \mathrm { k } } {/tex}

3.6{tex} \hat { \mathrm { j } } {/tex}

Explanation

Q 21.    

Correct4

Incorrect-1

If {tex} v _ { s } , v _ { x } {/tex} and {tex} v _ { m } {/tex} are the speed of soft gamma rays, X-rays and microwaves respectively in vacuum, then

A

{tex} \mathrm{v} _ { s } > \mathrm{v} _ { x } > \mathrm{v} _ { m } {/tex}

B

{tex} \mathrm { v } _ { \mathrm { s } } < \mathrm { v } _ { \mathrm { x } } < \mathrm { v } _ { \mathrm { m } } {/tex}

C

{tex} \mathrm { v } _ { \mathrm { s } } > \mathrm { v } _ { \mathrm { x } } < \mathrm { v } _ { \mathrm { m } } {/tex}

{tex} \mathrm{v} _ { s } = \mathrm{v} _ { x } = \mathrm{v} _ { m } {/tex}

Explanation

Q 22.    

Correct4

Incorrect-1

Photons of an electromagnetic radiation has an energy 11 keV each. To which region of electromagnetic spectrum does it belong?

X-ray region

B

Ultra violet region

C

Infrared region

D

Visible region

Explanation

Q 23.    

Correct4

Incorrect-1

A plane electromagnetic wave travels in free space along x-axis. At a particular point in space, the electric field along {tex} y{/tex}-axis is 9.3{tex} \mathrm { Vm } ^ { - 1 } {/tex} . The magnetic induction (B) along z-axis is

{tex} 3.1 \times 10 ^ { - 8 } \mathrm { T } {/tex}

B

{tex} 3 \times 10 ^ { - 5 } \mathrm { T } {/tex}

C

{tex} 3 \times 10 ^ { - 6 } \mathrm { T } {/tex}

D

{tex} 9.3 \times 10 ^ { - 6 } \mathrm { T } {/tex}

Explanation

Q 24.    

Correct4

Incorrect-1

The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating in vacuum is equal to:

A

the speed of light in vacuum

reciprocal of speed of light in vacuum

C

the ratio of magnetic permeability to the electric susceptibility of vacuum

D

unity

Explanation

Q 25.    

Correct4

Incorrect-1

A plane electromagnetic wave is incident on a material surface. If the wave delivers momentum {tex} \mathrm { p } {/tex} and energy {tex} \mathrm { E } {/tex} , then

A

{tex} \mathrm { p } = 0 , \mathrm { E } = 0 {/tex}

{tex} \mathrm { p } \neq 0 , \mathrm { E } \neq 0 {/tex}

C

{tex} \mathrm { p } \neq 0 , \mathrm { E } = 0 {/tex}

D

{tex} \mathrm { p } = 0 , \mathrm { E } \neq 0 {/tex}

Explanation