Electromagnetic Waves Test

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Electromagnetic Waves Test - 16

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Question 1
1 / -0

Which wave characteristic describes the product of the frequency and the wavelength?

A
Frequency

B
Amplitude

C
Wavelength

D
Velocity

E
Period

Solution

The relation between frequency $$f$$ and wavelength $$\lambda$$ is given by ,
$$v=f\lambda$$
it is clear that velocity $$v$$ of wave describes the product of frequency and wavelength.
Question 2
1 / -0

Who first proposed the light as electromagnetic wave ?

A
Thomas Young

B
Max planck

C
James Clerk Maxwell

D
Albert Einstein

Solution

In 1864, Maxwell predicted the existence of electromagnetic waves, the existence of which had not been confirmed before that time, and out of his prediction came the concept of light being a wave, or more specifically, a type of electromagnetic wave.

It is a wide intuition that Albert Einstein proposed the dual nature theory but is not correct.
Question 3
1 / -0

In electromagnetic wave, according to Maxwell, changing electric field gives _______.

A
stationary magnetic field

B
conduction current

C
eddy current

D
displacement current

Solution

By integral form of modified Maxwell's equations, we have:
$$\oint _{ \partial S } { B }\cdot d{ \ell }=\mu _{ 0 }\int _{ S } ({ J }+\epsilon _{ 0 }\dfrac { \partial { E } }{ \partial t } )\cdot d{ S }\, $$

Where the displacement current density is given by:
$${ J }_{ D }={ \epsilon }_{ 0 }\dfrac { \partial E }{ \partial t } $$

The above integral states that, the line integral of magnetic field around any loop is equal to $${ \mu }_{ 0 }$$ times the surface integral of the total current density (free current plus displacement current) over any open surface which has the loop as its boundary.
Thus, it is clearly seen that a changing electric field gives rise to displacement current.
Question 4
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In an electromagnetic wave

A
Power is equally transferred along electric and magnetic fields

B
Power is transmitted in a direction perpendicular to both the field

C
Power is transmitted along electric field

D
Power is transmitted along magnetic field

Solution

For electromagnetic waves $$\vec{E}$$ and $$\vec{B}$$ are always perpendicular to each other and perpendicular to the direction of propagation. The direction of propagation is the direction of $$\vec{E}\times \vec{B}$$.
The direction of propagation of the wave is the direction of propagation of its energy and power.
Hence, correct answer is option B.
Question 5
1 / -0

Solar radiation is

A
Transverse electromagnetic wave

B
Longitudinal electromagnetic wave

C
Stationary wave

D
None of the above

Solution

Solar radiation is radiant energy emitted by sun, particularly transverse electromagnetic energy wave. About half of the radiation is in the visible short-wave part of electromagnetic spectrum. The other half is mostly in the near-infrared part, with some in ultraviolet part of spectrum.
Question 6
1 / -0

In a parallel C-R network with a voltage source, the current flowing through resistor is _______ current and that flowing through the capacitor is ________ current.

A
conduction, displacement

B
displacement, conduction

C
displacement, displacement

D
conduction, conduction

Solution

In a parallel C-R circuit network with a voltage source, the current flowing through resistor is conduction current and that flowing through the capacitor is displacement current.
Question 7
1 / -0

The frequency of electromagnetic wave in free space is $$2$$ MHz. When it passes through a region of relative permittivity $$\varepsilon_r=4.0$$, then its wave length __________ & frequency ______________.

A
Becomes double, becomes half

B
Becomes double, remains constant

C
Become half, become double

D
Becomes half, remains constant

Solution

$$c=\dfrac{1}{\sqrt {\epsilon_o \mu_o}}$$
In a dielectric
$$v=\dfrac{1}{\sqrt {\epsilon_o \epsilon_r \mu_o \mu_r}}$$
$$v=\dfrac{1}{\sqrt {4\epsilon_o \mu_o} }$$
$$v=\dfrac{1}{2\sqrt {\epsilon_o \mu_o }}$$
$$v=c/2$$
Frequency does not change so wavelength should become halved to make velocity half fold.($$v=\nu \lambda$$)
Hence the correct option is (D).
Question 8
1 / -0

$$X-$$ray falling on a material

A
Exerts a force on it

B
Transfer energy to it

C
Transfers momentum to it

D
Transfers impules to it

Solution

The emitted X-rays transfer energy to the material on which it is falling.
Question 9
1 / -0

An electromagnetic radiation has an energy of 13.2 keV. Then the radiation belongs to the region of

A
visible light

B
ultraviolet

C
infrared

D
X-ray

Solution

Given : E = 13.2 keV

The wavelength of the radiation is given by;
$$\lambda( in \overset{o}{A})= \dfrac{hc}{E(ineV)}$$

$$= \dfrac{12400}{13.2 \times 10^3} = 0.939\overset{o}{A} \\\approx 1\overset{o}{A}$$

X-rays cover wavelengths ranging from about $$10^{-8} m (10 nm )$$ to $$10^{-13} m (10^{-4}nm)$$.

Electromagnetic radiation of energy 13.2 keV belongs to X-ray region of the electromagnetic spectrum.
Question 10
1 / -0

If the directions of electric and magnetic field vectors of a plane electromagnetic wave are along positive $$y$$-direction and positive $$z$$-direction respectively, then the direction of propagation of the wave is along:

A
positive $$z$$-direction

B
negative $$z$$-direction

C
negative $$y$$-direction

D
positive $$x$$-direction

E
negative $$x$$-direction

Solution

$$e=E\times B$$, direction of propagation is always perpendicular to plane of $$E$$ and $$B$$. It will be positive in $$x$$-direction.

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Re-Attempt Weekly Quiz Competition

Electromagnetic Waves Test - 16

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Electromagnetic Waves Test - 16

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SHARING IS CARING

Question 1

Frequency

Amplitude

Wavelength

Velocity

Period

Solution

Question 2

Thomas Young

Max planck

James Clerk Maxwell

Albert Einstein

Solution

Question 3

stationary magnetic field

conduction current

eddy current

displacement current

Solution

Question 4

Power is equally transferred along electric and magnetic fields

Power is transmitted in a direction perpendicular to both the field

Power is transmitted along electric field

Power is transmitted along magnetic field

Solution

Question 5

Transverse electromagnetic wave

Longitudinal electromagnetic wave

Stationary wave

None of the above

Solution

Question 6

conduction, displacement

displacement, conduction

displacement, displacement

conduction, conduction

Solution

Question 7

Becomes double, becomes half

Becomes double, remains constant

Become half, become double

Becomes half, remains constant

Solution

Question 8

Exerts a force on it

Transfer energy to it

Transfers momentum to it

Transfers impules to it

Solution

Question 9

visible light

ultraviolet

infrared

X-ray

Solution

Question 10

positive $$z$$-direction

negative $$z$$-direction

negative $$y$$-direction

positive $$x$$-direction

negative $$x$$-direction

Solution

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