Electromagnetic Waves Test 1

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Electromagnetic Waves Test 1

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Weekly Quiz Competition

Question 1
1 / -0

The speed of electromagnetic waves in free space is given by .
Here μ0 is ___________and ε0 is ________________ of free space.

A
permeability, permittivity

B
coercivity, permeability

C
permeability, susceptibility

D
permittivity, permeability

Solution

μ₀ is called the permeability of free space and similarly, ε₀ is called the permittivity of free space.
Question 2
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Which region in the electromagnetic spectrum will have the highest speed?

A
Radio

B
Visible

C
All the regions have same speed

D
Microwaves

Solution

All regions have the same speed.
The speed of a wave is not dependent upon its frequency and wavelength but rather upon the properties of the medium through which it travels.
Question 3
1 / -0

Which region in the electromagnetic spectrum has the highest frequency?

A
Frequency is same for the complete spectrum

B
Gamma Radiation Region

C
Radio

D
Visible

Solution

A gamma ray or gamma radiation is a penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy
Question 4
1 / -0

Electromagnetic waves constitute of

A
Electric and magnetic field varying in space and time sinusoidally and propagating through space such that the two fields are at 60 degrees to the direction of propagation.

B
Electric and magnetic field varying in space and time sinusoidally and propagating through space such that the two fields are perpendicular to the direction of propagation.

C
Electric and magnetic field varying in space and time tangentially and propagating through space such that the two fields are perpendicular to the direction of propagation.

D
Electric and magnetic field varying in space and time tangentially and propagating through space such that the two fields are at 60 degrees to the direction of propagation.

Solution

Maxwell predicted that an accelerated charge produces a sinusoidal time varying magnetic field, which in turn produces a sinusoidal time varying electric field. These two fields are mutually perpendicular to each other and sources of each other. They (fields) form an electromagnetic wave i.e. the wave that is propagated by simultaneous periodic variations of electric field and magnetic field intensity.
Question 5
1 / -0

In electromagnetic waves the ratio of amplitudes of electric field and magnetic field is equal to

A
(E₀ / 2B₀) = c

B
(E₀ / B₀)^1/2 = c

C
(2E₀ / B₀) = c

D
(E₀ / B₀) = c

Solution

In electromagnetic waves the ratio of amplitudes of electric field and magnetic field is equal to the velocity of the electromagnetic waves in free space.
(E₀/ B₀) = c
Question 6
1 / -0

Which statement is true about electromagnetic waves?

A
Electromagnetic waves are longitudinal in nature

B
Electromagnetic waves can travel through vacuum

C
Velocity of electromagnetic waves is 3 X 10⁹ m/s

D
Ratio of electric field and magnetic field in electromagnetic field is 2E_rms / B_rms

Solution

Properties:• Electromagnetic waves are propagated by oscillating electric and magnetic fields oscillating at right angles to each other. Hence (a) is incorrect.
• Electromagnetic waves travel with a constant velocity of 3 x 108 ms^-1 in vacuum. Hence (c) is incorrect.
• Electromagnetic waves need no medium of propagation. The energy from the sun is received by the earth through electromagnetic waves. Hence, correct answer is (b).
Question 7
1 / -0

Which of the following is not a use of electromagnetic wave?

A
In detection of invisible writing

B
In global warming

C
In greenhouses to keep plants warm

D
In warfare for looking through mist and fog

Solution

Electromagnetic waves are not used to determine global warming.
Question 8
1 / -0

Which colour of the visible spectrum has the greatest wavelength?

A
Blue

B
Yellow

C
Red

D
Violet

Solution

Red light has the lowest energy and is least scattered and has thus least frequency, thus we get that it has the largest wavelength. Similarly violet has maximum frequency.
Question 9
1 / -0

The electric field for an em wave is: E = E₀sin[(12 x 10¹⁵ t – 4 x 10⁷ x)]. What is the speed of the em waves?

A
48 x 10⁸ m / s

B
3 x 10⁸ m / s

C
4 x 10⁷ m / s

D
12 x 10¹⁵ m / s

Solution

V(velocity/speed)= ω/wave number (K)
V= 12×10¹⁵/4×10⁷
V=3×10⁸ m/s
Question 10
1 / -0

The wavelength of X-rays is of the order of:

A
1 mm

B
1 cm

C
1 angstrom

D
1 micron

Solution

X-ray wavelength is in range of 10−11m to 10−8m
So option C is correct.

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Electromagnetic Waves Test 1

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Electromagnetic Waves Test 1

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Question 1

permeability, permittivity

coercivity, permeability

permeability, susceptibility

permittivity, permeability

Solution

Question 2

Radio

Visible

All the regions have same speed

Microwaves

Solution

Question 3

Frequency is same for the complete spectrum

Gamma Radiation Region

Radio

Visible

Solution

Question 4

Electric and magnetic field varying in space and time sinusoidally and propagating through space such that the two fields are at 60 degrees to the direction of propagation.

Electric and magnetic field varying in space and time sinusoidally and propagating through space such that the two fields are perpendicular to the direction of propagation.

Electric and magnetic field varying in space and time tangentially and propagating through space such that the two fields are perpendicular to the direction of propagation.

Electric and magnetic field varying in space and time tangentially and propagating through space such that the two fields are at 60 degrees to the direction of propagation.

Solution

Question 5

(E0 / 2B0) = c

(E0 / B0)1/2 = c

(2E0 / B0) = c

(E0 / B0) = c

Solution

Question 6

Electromagnetic waves are longitudinal in nature

Electromagnetic waves can travel through vacuum

Velocity of electromagnetic waves is 3 X 109 m/s

Ratio of electric field and magnetic field in electromagnetic field is 2Erms / Brms

Solution

Question 7

In detection of invisible writing

In global warming

In greenhouses to keep plants warm

In warfare for looking through mist and fog

Solution

Question 8

Blue

Yellow

Red

Violet

Solution

Question 9

48 x 108 m / s

3 x 108 m / s

4 x 107 m / s

12 x 1015 m / s

Solution

Question 10

1 mm

1 cm

1 angstrom

1 micron

Solution

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(E₀ / 2B₀) = c

(E₀ / B₀)^1/2 = c

(2E₀ / B₀) = c

(E₀ / B₀) = c

Velocity of electromagnetic waves is 3 X 10⁹ m/s

Ratio of electric field and magnetic field in electromagnetic field is 2E_rms / B_rms

48 x 10⁸ m / s

3 x 10⁸ m / s

4 x 10⁷ m / s

12 x 10¹⁵ m / s