Solutions of Electromagnetic Waves Test 01

# Solutions of Electromagnetic Waves Test 01 - Class 12

``` Page 1

CBSE TEST PAPER-01
CLASS - XII PHYSICS (Electro magnetic waves)
Ans 1: It absorbs all the harmful ultraviolet radiations thus protecting us from reaching the
Ans 2: Microwaves are used in Radar.
Ans 3: (1) infra-red radiations are used to take photographs under foggy conditions.
(2) Infra-red radiations are used in revealing the secret writings on the ancient
walls.
Ans 4: (1) X -Rays
(2) Microwaves
Ans 5: (a)
O
O
E
C
B
=
O
O
E
B
C
=
8
60
3 10
=
×
Since magnetic field and electric field are ? to each other
? By = 2 × 10
-7
T sin
( )
3
11
10 3
10
2 2
t
x
? ?
+
? ?
? ?
---------------- (1)
Compare e.g. (1) with standard equation
By = B O sin 2
x t
T
p
?
? ?
+
? ?
? ?
( )
11
11
1 3
2 10
2
1 3 10
2 2
Also
T
T
p
?
p
=
×
= =
×
Ans 6: (a) V = 2 × 10
10
Hz
E O = 48 V/m
8
10
3 10
2 10
C
V
?
×
= =
×
B
O
= 2 ×10
-7
T
3
4 10 m ? p
- = ×
11
3
10
4
Hz ?
p
= ×
2
1.5 10 m ?
- = ×
Page 2

CBSE TEST PAPER-01
CLASS - XII PHYSICS (Electro magnetic waves)
Ans 1: It absorbs all the harmful ultraviolet radiations thus protecting us from reaching the
Ans 2: Microwaves are used in Radar.
Ans 3: (1) infra-red radiations are used to take photographs under foggy conditions.
(2) Infra-red radiations are used in revealing the secret writings on the ancient
walls.
Ans 4: (1) X -Rays
(2) Microwaves
Ans 5: (a)
O
O
E
C
B
=
O
O
E
B
C
=
8
60
3 10
=
×
Since magnetic field and electric field are ? to each other
? By = 2 × 10
-7
T sin
( )
3
11
10 3
10
2 2
t
x
? ?
+
? ?
? ?
---------------- (1)
Compare e.g. (1) with standard equation
By = B O sin 2
x t
T
p
?
? ?
+
? ?
? ?
( )
11
11
1 3
2 10
2
1 3 10
2 2
Also
T
T
p
?
p
=
×
= =
×
Ans 6: (a) V = 2 × 10
10
Hz
E O = 48 V/m
8
10
3 10
2 10
C
V
?
×
= =
×
B
O
= 2 ×10
-7
T
3
4 10 m ? p
- = ×
11
3
10
4
Hz ?
p
= ×
2
1.5 10 m ?
- = ×
(b) E O = cB O
8
48
3 10
O
O
E
B
C
= =
×
(c) Energy density
2
1
2
O
U E = ?
12
1
8.85 10 48 48
2
U
- = × × ×
Ans 7: V = 6 × 10
12
Hz
8
12
Using
3 10
6 10
c
v
?
?
=
×
=
×
Applications
(1) It keeps the earth warm.
(2) Infra-red lamps are used to treat muscular strains.
Ans 8: (a) The direction of propagation of wave is along + x – axis.
(b) Amplitude = 4 units
(c) Component of magnetic of field
8
4
3 10
Eo
Bz
C
= =
×
Ans 9: Characteristics of em waves
(1) It travels in free space with speed of light c = 3 x 10
8
m/s.
(2) Electromagnetic waves are transverse in nature.
Velocity of em waves in vacuum C =
1
o o
µ ?
8
16 10 Tesla
O
B
- = ×
U = 1 ×10
-8
J/m
3

5
5 10 m ?
- = ×
Bz = 1.33 ×10
-8
Tesla
```

## FAQs on Solutions of Electromagnetic Waves Test 01 - Class 12

 1. What are electromagnetic waves?
Ans. Electromagnetic waves are a form of energy propagation that consists of electric and magnetic fields oscillating perpendicular to each other and to the direction of wave propagation. These waves can travel through a vacuum or a medium and include various forms such as radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
 2. How do electromagnetic waves propagate?
Ans. Electromagnetic waves propagate through the interaction of electric and magnetic fields. The changing electric field generates a magnetic field, which in turn generates a changing electric field, creating a self-propagating cycle. These waves can travel in a straight line and at the speed of light, with different wavelengths and frequencies determining their characteristics.
 3. What is the relationship between frequency and wavelength of electromagnetic waves?
Ans. The frequency and wavelength of electromagnetic waves are inversely proportional. This means that as the frequency increases, the wavelength decreases, and vice versa. The formula that relates them is c = λν, where c is the speed of light, λ is the wavelength, and ν is the frequency. This relationship holds true for all electromagnetic waves.
 4. How do electromagnetic waves interact with matter?
Ans. Electromagnetic waves can interact with matter in various ways depending on their frequency. Lower frequency waves such as radio waves and microwaves can be absorbed, reflected, or transmitted by certain materials. Higher frequency waves like X-rays and gamma rays can penetrate matter and cause ionization or excitation of atoms and molecules. The interaction of electromagnetic waves with matter forms the basis for various technologies such as communication systems, medical imaging, and more.
 5. What are some practical applications of electromagnetic waves?
Ans. Electromagnetic waves have numerous practical applications in our daily lives. Some examples include: - Radio waves are used for broadcasting, communication, and wireless transmission. - Microwaves are used in cooking, radar systems, and satellite communication. - Infrared waves are used in remote controls, night vision devices, and thermal imaging. - Visible light enables us to see, and it is used in photography, optical communication, and illumination. - X-rays are utilized in medical imaging, security screening, and material analysis. - Gamma rays have applications in cancer treatment, sterilization, and industrial inspection.
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