EM Waves Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 Light is an electromagnetic wave. Its speed in vacuum is
given by the expression
(a)
oo
me (b)
o
o
m
e
(c)
o
o
e
m
(d)
oo
1
me
Q.2 The range of wavelength of the visible light is
(a) 10 Å to 100 Å
(b) 4,000 Å to 8,000 Å
(c) 8,000 Å to 10,000 Å
(d) 10,000 Å to 15000 Å
Q.3 Which of the following radiations has the least wavelength?
(a) g-rays (b) b-rays
(c) a-rays (d) X -rays
Q.4 A parallel plate capacitor with plate area A and seperation
between the plates d, is charged by a constant current i.
Consider a plane surface of area A/4 parallel to the plates
and drawn symetrically between the plates, what is the
displacement current through this area?
(a)i (b) 2i (c) i /4 (d) i/2
Q.5 The charging current for a capacitor is 1 A, then the
displacement current is
(a) 1 A (b) 0.5 A
(c)0 (d) 2 A
Page 2


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 Light is an electromagnetic wave. Its speed in vacuum is
given by the expression
(a)
oo
me (b)
o
o
m
e
(c)
o
o
e
m
(d)
oo
1
me
Q.2 The range of wavelength of the visible light is
(a) 10 Å to 100 Å
(b) 4,000 Å to 8,000 Å
(c) 8,000 Å to 10,000 Å
(d) 10,000 Å to 15000 Å
Q.3 Which of the following radiations has the least wavelength?
(a) g-rays (b) b-rays
(c) a-rays (d) X -rays
Q.4 A parallel plate capacitor with plate area A and seperation
between the plates d, is charged by a constant current i.
Consider a plane surface of area A/4 parallel to the plates
and drawn symetrically between the plates, what is the
displacement current through this area?
(a)i (b) 2i (c) i /4 (d) i/2
Q.5 The charging current for a capacitor is 1 A, then the
displacement current is
(a) 1 A (b) 0.5 A
(c)0 (d) 2 A
2
DPP/ P 48
Q.6 If E
r
 and B
r
 be the electric and magnetic field of E.M.
wave then the direction of propogation of E.M. wave is
along the direction.
(a) E
r
(b) B
r
(c) E
r
 × B
r
(d) B
r
 × E
r
Q.7 Which of the following pairs of space and time varying E
and B fields would generate a plane electromagnetic wave
travelling in (–Z) direction ?
(a)E
x
, B
y
(b)E
y
, B
x
(c)E
z
, B
y
(d)E
y
, B
z
Q.8 Choose the wrong statement for E.M. wave. They-
(a) are transverse
(b) travel in vacuum with the speed of light
(c) are produced by accelerated charges
(d) travel with same speed in all medium
Q.9 The intensity of light from a source is 500/p W/m
2
. Find
the amplitude of electric field in this wave-
(a)
3
 × 10
2 
N/C (b)2
3
 × 10
2
 N/C
(c)
3
2
 × 10
2
 N/C (d)2
3
 ×10
1 
N/C
Q.10A point source of 2 watt is radiating uniformly in all
direction in vacuum. Find the amplitude of electric field
at a distance 2m from it-
(a) 3 × 10
–4
(b)
30
(c)
3
 × 10
–4
(d)
3
 × 10
–2
Q.11 In a EM wave the amplitude of electric field is 10 V/m.
The frequency of wave is 5 × 10
4 
Hz. The wave is
propagating along Z-axis. Then the average energy density
of magnetic field is-
(a) 2.21 × 10
–10 
J/m
3
(b) 2.21 × 10
–8 
J/m
3
(c) 2 × 10
–8 
J/m
3
(d) 2 × 10
–10 
J/m
3
Q.12 Elecromagnetic waves travel in a medium with a speed of
2 × 10
8 
m/s. The relative permeability of the medium is 1.
What is the relative permittivity of the medium ?
(a) 2.25 (b) 1.25 (c) 3.25 (d) 0.25
Q.13 A magnetic field of a plane electromagnetic wave is given
by B
y
 = 2 × 10
–7 
sin(0.5 × 10
3
x + 1.5 × 10
11
t) T. Fequency
of the wave is
(a) 23.9 Hz (b) 13.9 Hz
(c) 33.9 Hz (d) 12.9 Hz
Q.14The electric field of a plane electromagnetic wave
in vacuum is represented by
E
x
 = 0, E
y 
= 0.5 cos[2p × 10
8 
(t – x/c)] and E
z 
= 0.
Determine the wavelength of the wave.
(a) 4 m (b) 5 m (c) 3 m (d) 6 m
Q.15 A light beam travelling in the X-direction is described by
the electric field E
y 
= (300 V/m)sinw(t – x/c). An electron
is constrained to move along the Y-direction with a speed
of 2.0 × 10
7 
m/s. Find the maximum magnetic force (in N)
on the electron.
(a) 3.2 × 10
–18
(b) 5.1 × 10
–16
(c) 6.5 × 10
–11
(d) 7.8 × 10
–12
Q.16 Which of the following waves have minimum frequency ?
(a) Microwaves (b) Audible waves
(c) Ultrasonic waves (d) Radiowaves
Q.17Electromagnetic waves travel in a medium which has
relative permeability 1.3 and relative permittivity 2.14.
Then the speed of the electromagnetic wave in the medium
will be
(a) 13.6 × 10
6
 m/s (b) 1.8 × 10
2
 m/s
(c) 3.6 × 10
8
 m/s (d) 1.8 × 10
8
 m/s
Q.18 If l
v
, l
x
 and l
m
 represent the wavelength of visible light
x-rays and microwaves respectively, then
(a) l
m
 > l
x
 > l
v
(b) l
v
 > l
m
 > l
x
(c) l
m
 > l
v
 > l
x
(d) l
v
 > l
x
 > l
m
Page 3


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 Light is an electromagnetic wave. Its speed in vacuum is
given by the expression
(a)
oo
me (b)
o
o
m
e
(c)
o
o
e
m
(d)
oo
1
me
Q.2 The range of wavelength of the visible light is
(a) 10 Å to 100 Å
(b) 4,000 Å to 8,000 Å
(c) 8,000 Å to 10,000 Å
(d) 10,000 Å to 15000 Å
Q.3 Which of the following radiations has the least wavelength?
(a) g-rays (b) b-rays
(c) a-rays (d) X -rays
Q.4 A parallel plate capacitor with plate area A and seperation
between the plates d, is charged by a constant current i.
Consider a plane surface of area A/4 parallel to the plates
and drawn symetrically between the plates, what is the
displacement current through this area?
(a)i (b) 2i (c) i /4 (d) i/2
Q.5 The charging current for a capacitor is 1 A, then the
displacement current is
(a) 1 A (b) 0.5 A
(c)0 (d) 2 A
2
DPP/ P 48
Q.6 If E
r
 and B
r
 be the electric and magnetic field of E.M.
wave then the direction of propogation of E.M. wave is
along the direction.
(a) E
r
(b) B
r
(c) E
r
 × B
r
(d) B
r
 × E
r
Q.7 Which of the following pairs of space and time varying E
and B fields would generate a plane electromagnetic wave
travelling in (–Z) direction ?
(a)E
x
, B
y
(b)E
y
, B
x
(c)E
z
, B
y
(d)E
y
, B
z
Q.8 Choose the wrong statement for E.M. wave. They-
(a) are transverse
(b) travel in vacuum with the speed of light
(c) are produced by accelerated charges
(d) travel with same speed in all medium
Q.9 The intensity of light from a source is 500/p W/m
2
. Find
the amplitude of electric field in this wave-
(a)
3
 × 10
2 
N/C (b)2
3
 × 10
2
 N/C
(c)
3
2
 × 10
2
 N/C (d)2
3
 ×10
1 
N/C
Q.10A point source of 2 watt is radiating uniformly in all
direction in vacuum. Find the amplitude of electric field
at a distance 2m from it-
(a) 3 × 10
–4
(b)
30
(c)
3
 × 10
–4
(d)
3
 × 10
–2
Q.11 In a EM wave the amplitude of electric field is 10 V/m.
The frequency of wave is 5 × 10
4 
Hz. The wave is
propagating along Z-axis. Then the average energy density
of magnetic field is-
(a) 2.21 × 10
–10 
J/m
3
(b) 2.21 × 10
–8 
J/m
3
(c) 2 × 10
–8 
J/m
3
(d) 2 × 10
–10 
J/m
3
Q.12 Elecromagnetic waves travel in a medium with a speed of
2 × 10
8 
m/s. The relative permeability of the medium is 1.
What is the relative permittivity of the medium ?
(a) 2.25 (b) 1.25 (c) 3.25 (d) 0.25
Q.13 A magnetic field of a plane electromagnetic wave is given
by B
y
 = 2 × 10
–7 
sin(0.5 × 10
3
x + 1.5 × 10
11
t) T. Fequency
of the wave is
(a) 23.9 Hz (b) 13.9 Hz
(c) 33.9 Hz (d) 12.9 Hz
Q.14The electric field of a plane electromagnetic wave
in vacuum is represented by
E
x
 = 0, E
y 
= 0.5 cos[2p × 10
8 
(t – x/c)] and E
z 
= 0.
Determine the wavelength of the wave.
(a) 4 m (b) 5 m (c) 3 m (d) 6 m
Q.15 A light beam travelling in the X-direction is described by
the electric field E
y 
= (300 V/m)sinw(t – x/c). An electron
is constrained to move along the Y-direction with a speed
of 2.0 × 10
7 
m/s. Find the maximum magnetic force (in N)
on the electron.
(a) 3.2 × 10
–18
(b) 5.1 × 10
–16
(c) 6.5 × 10
–11
(d) 7.8 × 10
–12
Q.16 Which of the following waves have minimum frequency ?
(a) Microwaves (b) Audible waves
(c) Ultrasonic waves (d) Radiowaves
Q.17Electromagnetic waves travel in a medium which has
relative permeability 1.3 and relative permittivity 2.14.
Then the speed of the electromagnetic wave in the medium
will be
(a) 13.6 × 10
6
 m/s (b) 1.8 × 10
2
 m/s
(c) 3.6 × 10
8
 m/s (d) 1.8 × 10
8
 m/s
Q.18 If l
v
, l
x
 and l
m
 represent the wavelength of visible light
x-rays and microwaves respectively, then
(a) l
m
 > l
x
 > l
v
(b) l
v
 > l
m
 > l
x
(c) l
m
 > l
v
 > l
x
(d) l
v
 > l
x
 > l
m
DPP/ P 48
3
Q.19Light wave is travelling along + y-direction. If the
corresponding E
r
 vector at that time is along + x-direction,
B
r
 vector must be directed along.
(a) y-axis
y
x
z
(b) x-axis
(c) + z-axis
(d) – z axis
Q.20 A wave is propagating in a medium of dielectric constant 2
and relative magnetic permeability 50. The wave impedance
of such a medium is
(a)5W (b) 376.6W
(c) 1883 W (d) 3776 W
DIRECTIONS (Q.21-Q.23) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct
(b) 1 and 2 are correct
(c) 2 and 4 are correct
(d) 1 and 3 are correct
Q.21 Which of the following statements are true ?
(1) Photographic plates are sensitive to ultraviolet rays.
(2) Photographic plates can be made sensitive to infrared
rays.
(3) Infrared rays are emitted by hot objects.
(4) Infrared photon has more energy than the photon of
visible light.
Q.22 Which of the following are electromagnetic  waves ?
(1) Cosmic rays (2) Gamma rays
(3) X-rays (4) b- rays
Q.23 An electromagnetic wave of frequency n = 3.0 MHz passes
from vacuum into a dielectric medium with permitivity
e = 4.0. Then the wrong statements are
(1) Wavelength is doubled and the frequency remains
unchanged
(2) Wavelength is doubled and frequency becomes half
(3) Wavelength and frequency both remain unchanged
(4) Wavelength is halved and frequency remains
unchanged
DIRECTIONS (Q.24-Q.26) : Read the passage given below
and answer the questions that follows :
The electron density of a layer of ionosphere at a height 150
km from the earth surface is 9 ×10
10
 per m
3
. For the sky wave
transmission from this layer upto a range of 250 km, find
Q.24The critical frequency of the layer
(a) 2.7 × 10
6
 Hz (b) 2.7 × 10
5 
Hz
(c) 4.7 × 10
6 
Hz (d) 4.8 × 10
5
Hz
Q.25 The maximum usuable frequency
(a) 3.17 × 10
8 
Hz (b) 3.17 × 10
6 
Hz
(c) 4.57 × 10
6 
Hz (d) 4.57 × 10
6
Hz
Q.26 The angle of incidence of this layer
(a) 34.5° (b) 25.2°
(c) 31.6° (d) 40°
DIRECTIONS (Q. 27-Q.29) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices,
only one of which is the correct answer. You have to select the
correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
Page 4


DIRECTIONS (Q.1-Q.20) : There are 20 multiple choice
questions. Each question has 4 choices (a), (b), (c) and (d), out
of which ONLY ONE choice is correct.
Q.1 Light is an electromagnetic wave. Its speed in vacuum is
given by the expression
(a)
oo
me (b)
o
o
m
e
(c)
o
o
e
m
(d)
oo
1
me
Q.2 The range of wavelength of the visible light is
(a) 10 Å to 100 Å
(b) 4,000 Å to 8,000 Å
(c) 8,000 Å to 10,000 Å
(d) 10,000 Å to 15000 Å
Q.3 Which of the following radiations has the least wavelength?
(a) g-rays (b) b-rays
(c) a-rays (d) X -rays
Q.4 A parallel plate capacitor with plate area A and seperation
between the plates d, is charged by a constant current i.
Consider a plane surface of area A/4 parallel to the plates
and drawn symetrically between the plates, what is the
displacement current through this area?
(a)i (b) 2i (c) i /4 (d) i/2
Q.5 The charging current for a capacitor is 1 A, then the
displacement current is
(a) 1 A (b) 0.5 A
(c)0 (d) 2 A
2
DPP/ P 48
Q.6 If E
r
 and B
r
 be the electric and magnetic field of E.M.
wave then the direction of propogation of E.M. wave is
along the direction.
(a) E
r
(b) B
r
(c) E
r
 × B
r
(d) B
r
 × E
r
Q.7 Which of the following pairs of space and time varying E
and B fields would generate a plane electromagnetic wave
travelling in (–Z) direction ?
(a)E
x
, B
y
(b)E
y
, B
x
(c)E
z
, B
y
(d)E
y
, B
z
Q.8 Choose the wrong statement for E.M. wave. They-
(a) are transverse
(b) travel in vacuum with the speed of light
(c) are produced by accelerated charges
(d) travel with same speed in all medium
Q.9 The intensity of light from a source is 500/p W/m
2
. Find
the amplitude of electric field in this wave-
(a)
3
 × 10
2 
N/C (b)2
3
 × 10
2
 N/C
(c)
3
2
 × 10
2
 N/C (d)2
3
 ×10
1 
N/C
Q.10A point source of 2 watt is radiating uniformly in all
direction in vacuum. Find the amplitude of electric field
at a distance 2m from it-
(a) 3 × 10
–4
(b)
30
(c)
3
 × 10
–4
(d)
3
 × 10
–2
Q.11 In a EM wave the amplitude of electric field is 10 V/m.
The frequency of wave is 5 × 10
4 
Hz. The wave is
propagating along Z-axis. Then the average energy density
of magnetic field is-
(a) 2.21 × 10
–10 
J/m
3
(b) 2.21 × 10
–8 
J/m
3
(c) 2 × 10
–8 
J/m
3
(d) 2 × 10
–10 
J/m
3
Q.12 Elecromagnetic waves travel in a medium with a speed of
2 × 10
8 
m/s. The relative permeability of the medium is 1.
What is the relative permittivity of the medium ?
(a) 2.25 (b) 1.25 (c) 3.25 (d) 0.25
Q.13 A magnetic field of a plane electromagnetic wave is given
by B
y
 = 2 × 10
–7 
sin(0.5 × 10
3
x + 1.5 × 10
11
t) T. Fequency
of the wave is
(a) 23.9 Hz (b) 13.9 Hz
(c) 33.9 Hz (d) 12.9 Hz
Q.14The electric field of a plane electromagnetic wave
in vacuum is represented by
E
x
 = 0, E
y 
= 0.5 cos[2p × 10
8 
(t – x/c)] and E
z 
= 0.
Determine the wavelength of the wave.
(a) 4 m (b) 5 m (c) 3 m (d) 6 m
Q.15 A light beam travelling in the X-direction is described by
the electric field E
y 
= (300 V/m)sinw(t – x/c). An electron
is constrained to move along the Y-direction with a speed
of 2.0 × 10
7 
m/s. Find the maximum magnetic force (in N)
on the electron.
(a) 3.2 × 10
–18
(b) 5.1 × 10
–16
(c) 6.5 × 10
–11
(d) 7.8 × 10
–12
Q.16 Which of the following waves have minimum frequency ?
(a) Microwaves (b) Audible waves
(c) Ultrasonic waves (d) Radiowaves
Q.17Electromagnetic waves travel in a medium which has
relative permeability 1.3 and relative permittivity 2.14.
Then the speed of the electromagnetic wave in the medium
will be
(a) 13.6 × 10
6
 m/s (b) 1.8 × 10
2
 m/s
(c) 3.6 × 10
8
 m/s (d) 1.8 × 10
8
 m/s
Q.18 If l
v
, l
x
 and l
m
 represent the wavelength of visible light
x-rays and microwaves respectively, then
(a) l
m
 > l
x
 > l
v
(b) l
v
 > l
m
 > l
x
(c) l
m
 > l
v
 > l
x
(d) l
v
 > l
x
 > l
m
DPP/ P 48
3
Q.19Light wave is travelling along + y-direction. If the
corresponding E
r
 vector at that time is along + x-direction,
B
r
 vector must be directed along.
(a) y-axis
y
x
z
(b) x-axis
(c) + z-axis
(d) – z axis
Q.20 A wave is propagating in a medium of dielectric constant 2
and relative magnetic permeability 50. The wave impedance
of such a medium is
(a)5W (b) 376.6W
(c) 1883 W (d) 3776 W
DIRECTIONS (Q.21-Q.23) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct
(b) 1 and 2 are correct
(c) 2 and 4 are correct
(d) 1 and 3 are correct
Q.21 Which of the following statements are true ?
(1) Photographic plates are sensitive to ultraviolet rays.
(2) Photographic plates can be made sensitive to infrared
rays.
(3) Infrared rays are emitted by hot objects.
(4) Infrared photon has more energy than the photon of
visible light.
Q.22 Which of the following are electromagnetic  waves ?
(1) Cosmic rays (2) Gamma rays
(3) X-rays (4) b- rays
Q.23 An electromagnetic wave of frequency n = 3.0 MHz passes
from vacuum into a dielectric medium with permitivity
e = 4.0. Then the wrong statements are
(1) Wavelength is doubled and the frequency remains
unchanged
(2) Wavelength is doubled and frequency becomes half
(3) Wavelength and frequency both remain unchanged
(4) Wavelength is halved and frequency remains
unchanged
DIRECTIONS (Q.24-Q.26) : Read the passage given below
and answer the questions that follows :
The electron density of a layer of ionosphere at a height 150
km from the earth surface is 9 ×10
10
 per m
3
. For the sky wave
transmission from this layer upto a range of 250 km, find
Q.24The critical frequency of the layer
(a) 2.7 × 10
6
 Hz (b) 2.7 × 10
5 
Hz
(c) 4.7 × 10
6 
Hz (d) 4.8 × 10
5
Hz
Q.25 The maximum usuable frequency
(a) 3.17 × 10
8 
Hz (b) 3.17 × 10
6 
Hz
(c) 4.57 × 10
6 
Hz (d) 4.57 × 10
6
Hz
Q.26 The angle of incidence of this layer
(a) 34.5° (b) 25.2°
(c) 31.6° (d) 40°
DIRECTIONS (Q. 27-Q.29) : Each of these questions contains
two statements: Statement-1 (Assertion) and Statement-2
(Reason). Each of these questions has four alternative choices,
only one of which is the correct answer. You have to select the
correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
4
DPP/ P 48
Q.27 Statement-1: The electromagnetic waves of shorter
wavelength can travel longer distances on earth's surface
than those of longer wavelengths.
Statement-2: Shorter the wavelength, the larger is the
velocity of wave propagation.
Q.28 Statement-1: Ultraviolet radiation are of higher frequency
waves  and are dangerous to human being.
Statement-2: Ultraviolet radiation are absorbed by the
atmosphere.
Q.29Statement-1: Radio waves can be polarised.
Statement-2: Sound waves in air are longitudinal in  nature.