CBSE Test Paper (Ray Optics) (Class - XII Physics) Class 12 Notes | EduRev

Class 12 : CBSE Test Paper (Ray Optics) (Class - XII Physics) Class 12 Notes | EduRev

 Page 1


CBSE TEST PAPER-02 
Class - XII Physics (Ray Optics) 
[ANSWERS] 
 Ans1: The image is produced due to regular reflection of light but when we read a newspaper, 
because of diffused (irregular) reflection of light we are not able to see even a faint 
image.  
Ans2: 
1
sin C
µ =
1
1
1
sin 45 2
o
µ = =
Ans3: the two rays from the object PQ undergoes 
total internal reflection firstly at the face  
AB and then at BC forming the find image  
' ' P Q (real and inverted image) 
Ans4: As we know ( )
1 2
1 1 1
1
f R R
µ
? ?
= - - ? ?
? ?
When R1 and R2 gets interchanged focal length of the lens remains the same hence 
position of the image will not change.  
Ans5:  At the surface AB 
1 1
i r d = - At the surface AC 
2 2
1 2
  
e r
Thus
d
d d d
= - = +
( )
1 2
(1) i e r r d = + - + - - - - 2 µ =
Page 2


CBSE TEST PAPER-02 
Class - XII Physics (Ray Optics) 
[ANSWERS] 
 Ans1: The image is produced due to regular reflection of light but when we read a newspaper, 
because of diffused (irregular) reflection of light we are not able to see even a faint 
image.  
Ans2: 
1
sin C
µ =
1
1
1
sin 45 2
o
µ = =
Ans3: the two rays from the object PQ undergoes 
total internal reflection firstly at the face  
AB and then at BC forming the find image  
' ' P Q (real and inverted image) 
Ans4: As we know ( )
1 2
1 1 1
1
f R R
µ
? ?
= - - ? ?
? ?
When R1 and R2 gets interchanged focal length of the lens remains the same hence 
position of the image will not change.  
Ans5:  At the surface AB 
1 1
i r d = - At the surface AC 
2 2
1 2
  
e r
Thus
d
d d d
= - = +
( )
1 2
(1) i e r r d = + - + - - - - 2 µ =
In quadrilateral AQOR 
( )
360
    90
o
o
A Q O R
But Q R each
? + ? + ? + ? =
? = ?
180 (2)
    
o
A O
Now in QOR
? ? + ? = - - - - ?
1 2
 180
         180 (3)
o
o
Q O R
or r r O
? + ? + ? =
+ + ? = - - - - - From (2) and (3) 
1
 (4) r r A + = - - - - - Substituting equation (4) in equation (1) 
d = i + e – A             Or
Ans6: Advantages 
(1) The image formed in reflecting type telescope is free from chromatic aberrations 
(2) The image formed is very bright due to its large light gathering power.  
NEWTONIAN TELESCOPE (REFLECTING TYPE) 
A + d = i + e 
Page 3


CBSE TEST PAPER-02 
Class - XII Physics (Ray Optics) 
[ANSWERS] 
 Ans1: The image is produced due to regular reflection of light but when we read a newspaper, 
because of diffused (irregular) reflection of light we are not able to see even a faint 
image.  
Ans2: 
1
sin C
µ =
1
1
1
sin 45 2
o
µ = =
Ans3: the two rays from the object PQ undergoes 
total internal reflection firstly at the face  
AB and then at BC forming the find image  
' ' P Q (real and inverted image) 
Ans4: As we know ( )
1 2
1 1 1
1
f R R
µ
? ?
= - - ? ?
? ?
When R1 and R2 gets interchanged focal length of the lens remains the same hence 
position of the image will not change.  
Ans5:  At the surface AB 
1 1
i r d = - At the surface AC 
2 2
1 2
  
e r
Thus
d
d d d
= - = +
( )
1 2
(1) i e r r d = + - + - - - - 2 µ =
In quadrilateral AQOR 
( )
360
    90
o
o
A Q O R
But Q R each
? + ? + ? + ? =
? = ?
180 (2)
    
o
A O
Now in QOR
? ? + ? = - - - - ?
1 2
 180
         180 (3)
o
o
Q O R
or r r O
? + ? + ? =
+ + ? = - - - - - From (2) and (3) 
1
 (4) r r A + = - - - - - Substituting equation (4) in equation (1) 
d = i + e – A             Or
Ans6: Advantages 
(1) The image formed in reflecting type telescope is free from chromatic aberrations 
(2) The image formed is very bright due to its large light gathering power.  
NEWTONIAN TELESCOPE (REFLECTING TYPE) 
A + d = i + e 
Ans7: fo + fe = 101    --------- (1) 
100
fo
M
fe
= = 
fo  = 100 fe ---------- (2)  
Substituting equation. (2) in equation (1) 
fe + 100fe = 101 
101fe = 101 
Substituting fe in equation (2) 
fo = 100 ×1 
Ans8:  (a) convex lens 
(b) 
1 1 1
U f ?
- =
   When U ? 8
1 1
f ?
= i.e
In the given graph f = 10cm. 
  ' '  
' ' '
(1)
ABC and A B C are similar
A B B C
AB BC
?
? = - - - -  ' '  
' ' '
DCF and A B F are similar
A B B F
DC FC
?
? =
( )
' ' ' ' '
(2)
A B B F A B
DC AB
DC FC AB
? = = - - - - = ?
fe = 1cm 
fo = 100cm
f ? =
Page 4


CBSE TEST PAPER-02 
Class - XII Physics (Ray Optics) 
[ANSWERS] 
 Ans1: The image is produced due to regular reflection of light but when we read a newspaper, 
because of diffused (irregular) reflection of light we are not able to see even a faint 
image.  
Ans2: 
1
sin C
µ =
1
1
1
sin 45 2
o
µ = =
Ans3: the two rays from the object PQ undergoes 
total internal reflection firstly at the face  
AB and then at BC forming the find image  
' ' P Q (real and inverted image) 
Ans4: As we know ( )
1 2
1 1 1
1
f R R
µ
? ?
= - - ? ?
? ?
When R1 and R2 gets interchanged focal length of the lens remains the same hence 
position of the image will not change.  
Ans5:  At the surface AB 
1 1
i r d = - At the surface AC 
2 2
1 2
  
e r
Thus
d
d d d
= - = +
( )
1 2
(1) i e r r d = + - + - - - - 2 µ =
In quadrilateral AQOR 
( )
360
    90
o
o
A Q O R
But Q R each
? + ? + ? + ? =
? = ?
180 (2)
    
o
A O
Now in QOR
? ? + ? = - - - - ?
1 2
 180
         180 (3)
o
o
Q O R
or r r O
? + ? + ? =
+ + ? = - - - - - From (2) and (3) 
1
 (4) r r A + = - - - - - Substituting equation (4) in equation (1) 
d = i + e – A             Or
Ans6: Advantages 
(1) The image formed in reflecting type telescope is free from chromatic aberrations 
(2) The image formed is very bright due to its large light gathering power.  
NEWTONIAN TELESCOPE (REFLECTING TYPE) 
A + d = i + e 
Ans7: fo + fe = 101    --------- (1) 
100
fo
M
fe
= = 
fo  = 100 fe ---------- (2)  
Substituting equation. (2) in equation (1) 
fe + 100fe = 101 
101fe = 101 
Substituting fe in equation (2) 
fo = 100 ×1 
Ans8:  (a) convex lens 
(b) 
1 1 1
U f ?
- =
   When U ? 8
1 1
f ?
= i.e
In the given graph f = 10cm. 
  ' '  
' ' '
(1)
ABC and A B C are similar
A B B C
AB BC
?
? = - - - -  ' '  
' ' '
DCF and A B F are similar
A B B F
DC FC
?
? =
( )
' ' ' ' '
(2)
A B B F A B
DC AB
DC FC AB
? = = - - - - = ?
fe = 1cm 
fo = 100cm
f ? =
Combining equation (1) & (2) 
' ' B C B F
BC BF
=
Using sign conventions 
'
' '
'
B C
BC U
B F B C FC
B F f
FC f
?
?
= +
= - = =
= + - = +
f
U f
f U fU
? ?
? ?
- ? =
- = - +
Divide by U? f
1 1 1
U f ?
- = +
Or 
Hence derived 
1 1 1
f U ?
= -
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