JEE Main > Electromagnetic Waves

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


Q 1.    

Correct4

Incorrect-1

Infrared radiation is detected by

A

spectrometer

pyrometer

C

nanometer

D

photometer

Explanation


Q 2.    

Correct4

Incorrect-1

Electromagnetic waves are transverse in nature is evident by

polarization

B

interference

C

reflection

D

diffraction

Explanation


Q 3.    

Correct4

Incorrect-1

Which of the following are not electromagnetic waves?

A

cosmic rays

B

gamma rays

{tex} \beta {/tex} -rays

D

X-rays.

Explanation

Q 4.    

Correct4

Incorrect-1

Consider telecommunication through optical fibres Which of the following statements is not true?

A

Optical fibres can be of graded refractive index.

Optical fibres are subject to electromagnetic interference from outside.

C

Optical fibres have extremely low transmission loss.

D

Optical fibres may have homogeneous core with a suitable cladding.

Explanation


Q 5.    

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

A

wavelength is doubled and the frequency remains unchanged

B

wavelength is doubled and frequency becomes half

wavelength is halved and frequency remains unchanged

D

wavelength and frequency both remain unchanged.

Explanation



Q 6.    

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

A

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

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

C

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

D

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

Explanation



Q 7.    

Correct4

Incorrect-1

If {tex} E {/tex} and {tex} B {/tex} are the electric and magnetic field vectors of electromagnetic waves then the direction of propagation of electromagnetic wave is along the direction of

A

{tex} \vec { E } {/tex}

B

{tex} \vec { B } {/tex}

{tex} \vec { E } \times \vec { B } {/tex}

D

None of these

Explanation

Q 8.    

Correct4

Incorrect-1

The charge on a parallel plate capacitor is varying as {tex} q = q _ { 0 } \sin 2 \pi \cdot n t {/tex} The plates are very large and close
together. Neglecting the edge effects, the displacement current through the capacitor is

A

{tex} \frac { q } { \varepsilon _ { 0 } A } {/tex}

B

{tex} \frac { q _ { 0 } } { \varepsilon _ { 0 } } \sin 2 \pi n t {/tex}

2{tex} \pi n q _ { 0 } \cos \pi n t {/tex}

D

{tex} \frac { 2 \pi n q _ { 0 } } { \varepsilon _ { 0 } } \cos 2 \pi n t {/tex}

Explanation

Q 9.    

Correct4

Incorrect-1

The value of magnetic field between plates of capacitor, at distance of 1{tex} \mathrm { m } {/tex} from centre where electric field varies by {tex} 10 ^ { 10 } \mathrm { V } / \mathrm { m } / \mathrm { s } {/tex} will be

A

5.56{tex} \mathrm { T } {/tex}

B

5.56{tex} \mu \mathrm { T } {/tex}

C

5.56{tex} \mathrm { mT } {/tex}

55.6{tex} \mathrm { nT } {/tex}

Explanation

Q 10.    

Correct4

Incorrect-1

The electromagnetic waves do not transport

A

Energy

Charge

C

Momentum

D

Information

Explanation

Q 11.    

Correct4

Incorrect-1

A capacitor is connected in an electric circuit. When key is pressed, the current in the circuit is

A

Zero

Maximum

C

Any transient value

D

Depends on capacitor used

Explanation

Q 12.    

Correct4

Incorrect-1

Displacement current is continuous

when electric field is changing in the circuit.

B

when magnetic field is changing in the circuit.

C

in both types of fields.

D

through wires and resistance only.

Explanation

Q 13.    

Correct4

Incorrect-1

Instantaneous displacement current 1 A in the space between the parallel plates of 1 {tex} \mu \mathrm { F } {/tex} capacitor can be estab
lished by changing the potential difference at the rate of

A

0.1{tex} \mathrm { V } / \mathrm { s } {/tex}

B

1{tex} \mathrm { V } / \mathrm { s } {/tex}

{tex} 10 ^ { 6 } \mathrm { V } / \mathrm { s } {/tex}

D

{tex} 10 ^ { - 6 } \mathrm { V } / \mathrm { s } {/tex}

Explanation

Q 14.    

Correct4

Incorrect-1

The magnetic field between the plates of a capacitor when {tex} r > R {/tex} is given by

A

{tex} \frac { \mu _ { 0 } I _ { D } r } { 2 \pi R ^ { 2 } } {/tex}

B

{tex} \frac { \mu _ { 0 } I _ { D } } { 2 \pi R } {/tex}

{tex} \frac { \mu _ { 0 } I _ { D } } { 2 \pi r } {/tex}

D

{tex} \mathrm { kwU } {/tex}

Explanation

Q 15.    

Correct4

Incorrect-1

The magnetic field between the plates of a capacitor is given by {tex} B = \frac { \mu _ { 0 } I r } { 2 \pi R ^ { 2 } } {/tex}

A

{tex} r \geq R {/tex}

B

{tex} r \leq R {/tex}

{tex} r < R {/tex}

D

{tex} r = R {/tex}

Explanation

Q 16.    

Correct4

Incorrect-1

The conduction current is the same as displacement current when the source is

A

{tex}\mathrm {AC} {/tex} only

{tex} \mathrm { DC } {/tex} only

C

{tex} \mathrm { Both } \mathrm { AC } {/tex} and {tex} \mathrm { DC } {/tex}

D

Neither for {tex} \mathrm { AC } {/tex} nor for {tex} \mathrm { DC } {/tex}

Explanation

Q 17.    

Correct4

Incorrect-1

The wave function (in S.I. units) for an electromag- netic wave is given as
{tex} \Psi ( x , t ) = 10 ^ { 3 } \sin \pi \left( 3 \times 10 ^ { 6 } x - 9 - 10 ^ { 14 } t \right) {/tex}
The speed of the wave as

A

{tex} 9 \times 10 ^ { 14 } \mathrm { m } / \mathrm { s } {/tex}

{tex} 3 \times 10 ^ { 8 } \mathrm { m } / \mathrm { s } {/tex}

C

{tex} 3 \times 10 ^ { 16 } \mathrm { m } / \mathrm { s } {/tex}

D

{tex} 3 \times 10 ^ { 7 } \mathrm { m } / \mathrm { s } {/tex}

Explanation

Q 18.    

Correct4

Incorrect-1

In the above problem, wavelength of the wave is

666{tex} \mathrm { nm } {/tex}

B

666{tex} \mathrm { A } {/tex}

C

666{tex} \mu \mathrm { m } {/tex}

D

6.66 {tex} \mathrm { nm } {/tex}

Explanation



Q 19.    

Correct4

Incorrect-1

The Maxwell's four equations are written as
(i) {tex} \oint \vec { E } \cdot \overrightarrow { d s } = \frac { q _ { 0 } } { \varepsilon _ { 0 } } {/tex}
(ii) {tex} \oint \vec { B } \cdot \overrightarrow { d s } = 0 {/tex}
(iii) {tex} \oint \vec { E } \cdot \overrightarrow { d l } = \frac { d } { d t } \oint \vec { B } \cdot \overrightarrow { d s } {/tex}
(iv) {tex} \oint \vec { B } \cdot \overrightarrow { d s } = \mu _ { 0 } \varepsilon _ { 0 } \frac { d } { d t } \oint \vec { E } \cdot \overrightarrow { d s } {/tex}
The equations which have sources of {tex} \vec { E } {/tex} and {tex} \vec { B } {/tex}

A

(i), (ii) and (iii)

B

(i) and (ii)

C

(i) and (iii)

(i) and (iv)

Explanation

Q 20.    

Correct4

Incorrect-1

Out of the above four equations which do not contain source field are

A

(i) and (ii)

(ii) Only

C

All of four

D

(iii) Only

Explanation

Q 21.    

Correct4

Incorrect-1

Out of four Maxwell's equations above, which one shows non-existence of monopoles?

A

(i) and (iv)

(ii) Only

C

(iii) Only

D

(i) Only

Explanation

Q 22.    

Correct4

Incorrect-1

Which of the above Maxwell's equations shows that electric field lines do not form closed loops?

(i) only

B

(ii) only

C

(iii) only

D

(iv) only

Explanation

Q 23.    

Correct4

Incorrect-1

In an electromagnetic wave the average energy density is associated with

A

electric field only.

B

magnetic field only

equally with electric and magnetic fields.

D

average energy density is zero

Explanation

Q 24.    

Correct4

Incorrect-1

In an electromagnetic wave the average energy density associated with magnetic field will be

A

{tex} \frac { 1 } { 2 } L I ^ { 2 } {/tex}

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

C

{tex} \frac { 1 } { 2 } \mu _ { 0 } B ^ { 2 } {/tex}

D

{tex} \frac { 1 } { 2 } \frac { q } { B ^ { 2 } } {/tex}

Explanation

Q 25.    

Correct4

Incorrect-1

In the above problem, the energy density associated with the electric field will be

A

{tex} \frac { 1 } { 2 } C V ^ { 2 } {/tex}

B

{tex} \frac { 1 } { 2 } \frac { q ^ { 2 } } { C } {/tex}

C

{tex} \frac { 1 } { 2 } \frac { \varepsilon ^ { 2 } } { E } {/tex}

{tex} \frac { 1 } { 2 } \varepsilon _ { 0 } E ^ { 2 } {/tex}

Explanation