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# 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)
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)
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 =
( )
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
(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)
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 =
( )
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
(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)
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 =
( )
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
(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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