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# Solutions of Electromagnetic Waves Test 01 Class 12 Notes | EduRev

## Class 12 : Solutions of Electromagnetic Waves Test 01 Class 12 Notes | EduRev

``` 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
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