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

 Page 1


CBSE TEST PAPER-02 
CLASS - XII PHYSICS (Electro magnetic waves) 
[ANSWERS] 
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) 
[ANSWERS] 
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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