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# CBSE Test Paper (Electro magnetic waves) (Class - XII Physics) Class 12 Notes | EduRev

## Class 12 : CBSE Test Paper (Electro magnetic waves) (Class - XII Physics) Class 12 Notes | EduRev

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CBSE TEST PAPER-02
CLASS - XII PHYSICS (Electro magnetic waves)
Ans 1: Displacement current remains the same as charging current and is equal to 0.25A.
Ans 2: X – rays, Red light, Microwaves and Radio waves.
Ans 3: There is no effect on the frequency of ultraviolet light.
Ans 4: One.
Ans 5: Television signals are not reflected back by the layer of atmosphere called
ionosphere thus TV signals from air earth station are reflected back to the earth by
means of an artificial satellite
Ans 6: The infra-red radiations get trapped inside the earth’s atmosphere due to green
house effect which makes the earth warm. Therefore average temperature of the
earth would have been low.
Ans 7: Sky waves are not used in transmitting TV signals as they are not reflected by the
ionosphere.
Methods of increasing range of TV transmission
(1) Tall antenna
(2) Geostationary satellites
Ans 8: Since d = 2hR
If height is increased distance upto which TV coverage can be done will increases.
Ans 9: (a) The equation Ey = 0.5 cos  ( )
8
2 10 / t x c p ? ? × - ? ?
Represents wave is propagating along + x – axis
(b) Comparing equation with the standard one
Ey = E O cos w ( ) / t x c -
8
8
8
8
8
2 10
2 2 10
10
3 10
10
w
c
v
p
p? p
?
?
= ×
= ×
=
×
? = =
(c) Associated magnetic field is ? to electric field and the direction of propagation.
Since wave is propagating along x – axis, electric field is along, y – axis
Thus, magnetic field is along z – axis
3m ? =
Page 2

CBSE TEST PAPER-02
CLASS - XII PHYSICS (Electro magnetic waves)
Ans 1: Displacement current remains the same as charging current and is equal to 0.25A.
Ans 2: X – rays, Red light, Microwaves and Radio waves.
Ans 3: There is no effect on the frequency of ultraviolet light.
Ans 4: One.
Ans 5: Television signals are not reflected back by the layer of atmosphere called
ionosphere thus TV signals from air earth station are reflected back to the earth by
means of an artificial satellite
Ans 6: The infra-red radiations get trapped inside the earth’s atmosphere due to green
house effect which makes the earth warm. Therefore average temperature of the
earth would have been low.
Ans 7: Sky waves are not used in transmitting TV signals as they are not reflected by the
ionosphere.
Methods of increasing range of TV transmission
(1) Tall antenna
(2) Geostationary satellites
Ans 8: Since d = 2hR
If height is increased distance upto which TV coverage can be done will increases.
Ans 9: (a) The equation Ey = 0.5 cos  ( )
8
2 10 / t x c p ? ? × - ? ?
Represents wave is propagating along + x – axis
(b) Comparing equation with the standard one
Ey = E O cos w ( ) / t x c -
8
8
8
8
8
2 10
2 2 10
10
3 10
10
w
c
v
p
p? p
?
?
= ×
= ×
=
×
? = =
(c) Associated magnetic field is ? to electric field and the direction of propagation.
Since wave is propagating along x – axis, electric field is along, y – axis
Thus, magnetic field is along z – axis
3m ? =
8
8
0, 0
cos[2 10 ( / )]
cos 2 10 ( / )]
O
O
Bx By
Bz B t x x
E
Bz t x x
c
p
p
? = =
= × - = × -
Ans 10: Using C =  ??
19
8
19
11 12
= 5 10 Hz
3 10
=
5 10
0.6 10 6 10 m
?
?
?
- - ×
×
×
= × = ×
These are Gamma Rays.
Applications
(1) These rays are used to get information regarding atomic structure.
(2) They have very high penetrating power so they are used for detection purpose
Ans 11:  (1)  Frequency of the microwaves must be equal to the resonant frequency of the
water    molecules present in the food item.
(2)  (a) visible light
(b) Microwaves
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