Electromagnetic Waves — DPP 2

20 NEET questions from Electromagnetic Waves, with answers and explanations. Attempt it as a timed test to get scoring, accuracy breakdown and mistake tracking.

Attempt this test free 20 questions · 30 minutes · +80 marks
1
The cross product of electric and magnetic field gives
  1. A Direction of EM wave propagation
  2. B Speed of light
  3. C Null vector
  4. D All of these
Show answer & explanation

Correct answer: A

$\vec{V}=\vec{E} \times \vec{B}$
2
To establish an instantaneous displacement current of I ampere in the space between the plates of a parallel plate capacitor of capacitance $\frac { 1 } { 2 } \mathrm {~F}$, the value of $\frac { d V } { d t }$ is
  1. A 2I
  2. B $\frac { I } { 2 }$
  3. C $\frac { 1 } { 2 l }$
  4. D I
Show answer & explanation

Correct answer: A

Electromagnetic Waves – NEET-13344
3
5% of the power of 100 W bulb is converted to visible radiation. Average intensity of visible radiation at a distance of 10 m from the bulb is
  1. A $\frac { 5 } { 2 \pi ( 10 ) ^ { 2 } } \mathrm {~W} / \mathrm { m } ^ { 2 }$
  2. B $\frac { 5 } { 4 \pi ( 10 ) ^ { 2 } } \mathrm {~W} / \mathrm { m } ^ { 2 }$
  3. C $\frac { 5 } { \pi ( 10 ) ^ { 2 } } \mathrm {~W} / \mathrm { m } ^ { 2 }$
  4. D $\frac { 5 } { 8 \pi ( 10 ) ^ { 2 } } \mathrm {~W} / \mathrm { m } ^ { 2 }$
Show answer & explanation

Correct answer: B

Electromagnetic Waves – NEET-13351
4
If $\vec { E }$ and $\vec { B }$ are the electric and magnetic field vectors of electromagnetic wave then the direction of propagation of wave is along the direction of
  1. A $\vec { E }$
  2. B $\vec { B }$
  3. C $\vec { E } \times \vec { B }$
  4. D $\vec { B } \times \vec { E }$
Show answer

Correct answer: C

5
A plane electromagnetic wave is incident on a plane surface of area A normally, and is perfectly reflected. If energy E strikes the surface in time t then average pressure exerted on the surface is (c = speed of light)
  1. A Zero
  2. B $\frac { E } { \text { Atc } }$
  3. C $\frac { 2 E } { A t c }$
  4. D $\frac { E } { C }$
Show answer & explanation

Correct answer: C

Electromagnetic Waves – NEET-13350
6
A capacitor is connected across a battery which delivers a current of 1 A at an instant in the capacitor. Displacement current through the capacitor at that instant is
  1. A 1 A
  2. B 0 A
  3. C 2 A
  4. D $\frac { 1 } { 2 } \mathrm {~A}$
Show answer & explanation

Correct answer: A

$\begin{array}{l}I=1 \mathrm{~A} \\ I_{d}=I_{C}=1 \mathrm{~A}\end{array}$
7
If the electric field and magnetic field of an electromagnetic wave are related as $B = \frac { E } { C }$, where the symbols have their usual meanings and the energy in a given volume of space due to the electric field part is U, then the energy due to the magnetic field part will be
  1. A $\frac { U } { C }$
  2. B $\frac { U } { c ^ { 2 } }$
  3. C $\frac { U } { 2 }$
  4. D U
Show answer & explanation

Correct answer: D

Electromagnetic Waves – NEET-13347
8
The separation between the plate of a parallel plate capacitor is 1 mm is connected in an electric circuit if rate of change of voltage between the plate is $10 ^ { 8 } \mathrm {~V} / \mathrm { s }$ and plate area is $30 \mathrm {~cm} ^ { 2 }$, then the value of displacement current between the plate will be
  1. A 8.85 mA
  2. B 3.65 mA
  3. C 2.65 mA
  4. D 9.57 mA
Show answer & explanation

Correct answer: C

Electromagnetic Waves – NEET-13382
9
A plane electromagnetic wave of frequency 28 MHz travels in free space along the positive x-direction. At a particular point in space and time, electric field is 9.3 V/m along positive y-direction. The magnetic field (in T) at that point is
  1. A $3.1 \times 10 ^ { - 8 }$ along positive $z$-direction
  2. B $3.1 \times 10 ^ { - 8 }$ along negative $z$-direction
  3. C $3.2 \times 10 ^ { 7 }$ along positive $z$-direction
  4. D $3.2 \times 10 ^ { 7 }$ along negative $z$-direction
Show answer & explanation

Correct answer: A

Electromagnetic Waves – NEET-13349
10
An electromagnetic wave is propagating in vacuum along z-axis, the electric field component is given by $E _ { x } = E _ { 0 } \sin ( k z - \omega t )$, then magnetic component is
  1. A $B _ { x } = \frac { E _ { 0 } } { C } \sin ( k z - \omega t )$
  2. B $B _ { y } = \frac { B _ { 0 } } { C } \sin ( k z - \omega t )$
  3. C $B _ { y } = \frac { E _ { 0 } } { C } \sin ( k z - \omega t )$
  4. D $B _ { y } = B _ { 0 } C \sin ( k z - \omega t )$
Show answer & explanation

Correct answer: C

Electromagnetic Waves – NEET-13146
11
The direction of poynting vector represents
  1. A The direction of electric field
  2. B The direction of magnetic field
  3. C The direction of propagation of EM wave
  4. D The direction opposite to the propagation of EM wave
Show answer & explanation

Correct answer: C

Electromagnetic Waves – NEET-13345
12
The speed of electromagnetic waves depends upon
  1. A Wavelength
  2. B Frequency
  3. C Intensity
  4. D Medium, in which it travels
Show answer & explanation

Correct answer: D

Speed of wave = $\frac{1}{\sqrt{\mu \varepsilon}}$ = $\frac{l}{\sqrt{\mu_{0} \mu_{r} \varepsilon_{0} \varepsilon_{r}}}$
It depends upon the medium.
13
Dimensions of $\frac { 1 } { \sqrt { \mu _ { 0 } \varepsilon _ { 0 } } }$, where symbols have their usual meanings, are
  1. A $\left[ \mathrm { MLT } ^ { - 1 } \right]$
  2. B $\left[ \mathrm { M } ^ { 0 } \mathrm {~L} ^ { - 1 } \mathrm {~T} ^ { 1 } \right]$
  3. C $\left[ \mathrm { M } ^ { 0 } \mathrm { LT } ^ { - 1 } \right]$
  4. D $\left[ \mathrm { M } ^ { 0 } \mathrm {~L} ^ { 1 } \mathrm {~T} ^ { 1 } \right]$
Show answer & explanation

Correct answer: C

$C=\frac{1}{\sqrt{\mu_{0} \varepsilon_{0}}}$
14
During the propagation of a electromagnetic wave the phase difference between oscillating electric and magnetic field vector is
  1. A $90 ^ { \circ }$
  2. B Zero
  3. C $45 ^ { \circ }$
  4. D $60 ^ { \circ }$
Show answer & explanation

Correct answer: B

Both $\vec{E}$ and $\vec{B}$ are in same phase
15
To establish an instantaneous displacement current of 1 A in the space between two parallel plates of capacitor of capacitance 2μF, the potential difference across the capacitor plates will have to be changed at the rate of
  1. A $2 \times 10 ^ { 6 } \mathrm {~V} / \mathrm { s }$
  2. B $2 \times 10 ^ { 5 } \mathrm {~V} / \mathrm { s }$
  3. C $5 \times 10 ^ { 6 } \mathrm {~V} / \mathrm { s }$
  4. D $5 \times 10 ^ { 5 } \mathrm {~V} / \mathrm { s }$
Show answer & explanation

Correct answer: D

Electromagnetic Waves – NEET-13372
16
Which of the following has highest penetrating power?
  1. A γ-ray
  2. B UV-ray
  3. C Infrared ray
  4. D Microwave ray
Show answer

Correct answer: A

17
At a particular instant the current in the circuit given below is i. The displacement current between the plates of the capacitor shown below is
Electromagnetic Waves – NEET-13342
  1. A Zero
  2. B i
  3. C $\frac { i } { 2 }$
  4. D $\frac { i } { 4 }$
Show answer & explanation

Correct answer: B

Displacement current $i_{d}=i$
18
A plane electromagnetic wave of frequency 300 MHz travels in free space. The wavelength of the wave is
  1. A 100 cm
  2. B 25 cm
  3. C 50 cm
  4. D 75 cm
Show answer & explanation

Correct answer: A

$\begin{array}{l}c=f \lambda \\ 3 \times 10^{8}=300 \times 10^{6} \times \lambda \\ \lambda=1 \mathrm{~m}\end{array}$
19
Which of the following physical quantities contained in a small volume oscillates at double the frequency of passing electromagnetic wave?
  1. A Electric field
  2. B Magnetic field
  3. C Magnetic energy
  4. D All of these
Show answer & explanation

Correct answer: C

The electric and magnetic energy oscillate at double the frequency as compared to electric and magnetic field.
20
The wavelength of the oscillatory magnetic field in a plane electromagnetic wave given by $B _ { y } = 0.6 \times 10 ^ { - 5 } \sin \left( 4000 \pi x - 5 \times 10 ^ { 10 } \pi t \right) T$ is (where $x$ is meter and $t$ is in second)
  1. A $0.4 \times 10 ^ { - 3 } \mathrm {~m}$
  2. B $0.2 \times 10 ^ { - 3 } \mathrm {~m}$
  3. C $0.5 \times 10 ^ { - 3 } \mathrm {~m}$
  4. D $0.3 \times 10 ^ { - 3 } \mathrm {~m}$
Show answer & explanation

Correct answer: C

$\begin{array}{l}\frac{2 \pi}{\lambda}=4000 \pi \\ \Rightarrow \lambda=0.5 \times 10^{-3} \mathrm{~m}\end{array}$

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