Electromagnetic Waves Test

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Electromagnetic Waves Test - 31

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Weekly Quiz Competition

Question 1
1 / -0

Electromagnetic weave of frequency $$6 \times 10^{12}$$ Hz are traveling through free space. In which region of the e. m. spectrum, the waves will life?

A
Ultraviolet region

B
Infrared region

C
Microwave region

D
Visible region

Solution
Question 2
1 / -0

A light beam travelling in the x-direction is described by the electric field $${E_y} = 300v/m\sin \left( {t - \frac{x}{c}} \right)$$. An electron is constrained to move along the y-direction with a speed of $$2.0 \times {10^7}m/s.$$ Find the maximum magnetic force on the electron.

A
$$2 \times {10^{ - 18}}$$

B
$$2.5 \times {10^{ - 18}}$$

C
$$3 \times {10^{ - 18}}$$

D
$$3.2 \times {10^{ - 18}}$$

Solution

As we know that,
$${ B }_{ \circ }=\dfrac { { E }_{ \circ } }{ C } $$
Where,
$${ B }_{ \circ }$$ = Max. Magnetic Field
$${ E }_{ \circ }$$ = Max. Electric Field
C= speed of light
It is given that,
$${ E }_{ \circ }$$= 300 V/m
So, $${ B }_{ \circ }$$=$$\dfrac { 300 }{ 3\times { 10 }^{ 8 } }$$ = $${ 10 }^{ -6 }$$ T
Now, maximum magnetic force= qv$${ B }_{ \circ }$$
= $$1.6\times { 10 }^{ -19 }\times 2\times { 10 }^{ 7 }\times { 10 }^{ -6 }$$
=$$3.2\times { 10 }^{ -18 }$$ N
Question 3
1 / -0

A magnetic field can be produced by

A
a moving charge

B
a changing electric field

C
none of them

D
both of them

Solution
Question 4
1 / -0

If at a certain instant, the magnetic induction of the electromagnetic wave in vacuum is $$6.7\times 10^{-12}T$$, then the magnitude of electric field intensity will be?

A
$$2\times 10^{-3}$$N/C

B
$$3\times 10^{-3}$$N/C

C
$$4\times 10^{-3}$$N/C

D
$$1\times 10^{-3}$$N/C

Solution
Question 5
1 / -0

Mark the correct option in impure spectrum :

A
Order of colours is reverse

B
Order of colours is irregular

C
colours are overlapped

D
no colours is present
Solution
For impure spectrum:
1. The order of colours is are straight, hence option a is false
2. Order of colours are regular
3. Colours are overlapped each other in impure spectrum
4. Colours are present in impure spectrum
Hence option C is the correct statement according to the impure spectrum
Question 6
1 / -0

The electric field portion of an electromagnetic wave is given by(all variables in SI units) $$E=10^{-4}\sin(6\times 10^5t-0.01x)$$. The frequency (f) and the speed(v) of electromagnetic wave are?

A
$$f=\dfrac{30}{\pi}kHz$$ and $$v=1.5\times 10^7m/s$$

B
$$f=\dfrac{90}{\pi}kHz$$ and $$v=6.0\times 10^7m/s$$

C
$$f=\dfrac{300}{\pi}kHz$$ and $$v=6.0\times 10^7m/s$$

D
$$f=\dfrac{600}{\pi}kHz$$ and $$v=7.5\times 10^7m/s$$

E
$$f=\dfrac{900}{\pi}kHz$$ and $$v=8.0\times 10^7m/s$$

Solution

$$\omega =6\times 10^5=2\pi f$$
$$f=\dfrac{6}{2\pi}\times 10^5=\dfrac{3}{\pi}\times 10^5Hz$$
$$=\dfrac{300}{\pi}\times 10^3Hz$$
$$=\dfrac{300}{\pi}kHz$$
Wave speed, $$v=\dfrac{\omega}{k}$$
$$\Rightarrow\dfrac{6\times 10^5}{0.01}=6\times 10^7m/s$$.
So, the correct option is $$(C)$$
Question 7
1 / -0

An electric field $$\vec {E}$$ and a magnetic field $$\vec{B}$$ exist in the region. The fields are not perpendicular to each other

A
This is not possible

B
No electromagnetic wave passing through the region

C
An electromagnetic wave may is passing through the region

D
An electromagnetic wave certainly passing through the region

Solution
Question 8
1 / -0

The electric field 'E' and magnetic field 'B' in electromagnetic waves are?

A
Parallel to each other

B
Inclined at an angle of $$45^o$$

C
Perpendicular to each other

D
Opposite to each other

Solution
Question 9
1 / -0

Microwaves from a transmitter are directed normally towards a plane reflector. A detector moves along the normal to the reflector. Between positions of $$14$$ successive maxima the detector travels a distance $$0.14 m$$. The frequency of the transmitter is $$(c=3 \times 10_{8} m/s)$$

A
$$1.5 \times 10^{10} Hz$$

B
$$10^{10}Hz$$

C
$$3 \times 10^{10} Hz$$

D
$$6 \times 10^{10} Hz$$

Solution

The detector receives direct as well as reflected waves. The distance moved between two consecutive position of maxima is $$\lambda/2$$.
$$14 \times \dfrac{\lambda}{2}= 71= 0.14 m$$
$$\Rightarrow \lambda = 0.02m$$
$$ c=n\lambda$$
Putting $$c = 3 \times 10^{8} m/s,$$ we
have
$$n =\dfrac{c}{\lambda}= \dfrac{3 \times 10^{8}}{0.02}=1.5 \times 10^{10} Hz$$
Question 10
1 / -0

An electromagnetic wave, going through vacuum is described by $$E=E_0 \sin (kx -\omega t)$$. Which of the following is independent of wavelength

A
$$k$$

B
$$\omega$$

C
$$k/\omega$$

D
$$k\omega$$

Solution

The angular wave number $$k=\dfrac {2\pi}{\lambda}$$, where $$\lambda$$ is the wave length. The angular frequency is $$w=2\pi v$$
The ratio $$\dfrac {k}{\omega}=\dfrac {2\pi / \lambda}{2\pi v}=\dfrac {1}{v \pi}=\dfrac {1}{c}=$$ constant

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Electromagnetic Waves Test - 31

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Electromagnetic Waves Test - 31

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Question 1

Ultraviolet region

Infrared region

Microwave region

Visible region

Solution

Question 2

$$2 \times {10^{ - 18}}$$

$$2.5 \times {10^{ - 18}}$$

$$3 \times {10^{ - 18}}$$

$$3.2 \times {10^{ - 18}}$$

Solution

Question 3

a moving charge

a changing electric field

none of them

both of them

Solution

Question 4

$$2\times 10^{-3}$$N/C

$$3\times 10^{-3}$$N/C

$$4\times 10^{-3}$$N/C

$$1\times 10^{-3}$$N/C

Solution

Question 5

Order of colours is reverse

Order of colours is irregular

colours are overlapped

no colours is present

Solution

Question 6

$$f=\dfrac{30}{\pi}kHz$$ and $$v=1.5\times 10^7m/s$$

$$f=\dfrac{90}{\pi}kHz$$ and $$v=6.0\times 10^7m/s$$

$$f=\dfrac{300}{\pi}kHz$$ and $$v=6.0\times 10^7m/s$$

$$f=\dfrac{600}{\pi}kHz$$ and $$v=7.5\times 10^7m/s$$

$$f=\dfrac{900}{\pi}kHz$$ and $$v=8.0\times 10^7m/s$$

Solution

Question 7

This is not possible

No electromagnetic wave passing through the region

An electromagnetic wave may is passing through the region

An electromagnetic wave certainly passing through the region

Solution

Question 8

Parallel to each other

Inclined at an angle of $$45^o$$

Perpendicular to each other

Opposite to each other

Solution

Question 9

$$1.5 \times 10^{10} Hz$$

$$10^{10}Hz$$

$$3 \times 10^{10} Hz$$

$$6 \times 10^{10} Hz$$

Solution

Question 10

$$k$$

$$\omega$$

$$k/\omega$$

$$k\omega$$

Solution

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