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Class 12
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Physics
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Ray Optics and Optical Instruments
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Combination of Mirror and Lenses
Combination of Mirror and Lenses
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Calculation of Focal Length for Combination of Mirror and Lens
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Object and Lens Placed in Water
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Problems in Lenses and Mirrors - Problem L1
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Combination of Lenses and Mirrors
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Important Questions
A concave lens of focal length 15cm forms an image 10 cm from the lens . How far is the object placed from the lens? Draw the ray diagram.
Medium
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>
A beam of light converges at a point P. Now a lens is placed in the path of the convergent beam
1
2
cm from P. At what point does the beam converge if the lens is (a) a convex lens of focal length
2
0
cm, and (b) a concave lens of focal length
1
6
cm?
Hard
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>
A convex lens
A
of focal length
2
0
c
m
and a concave lens
B
of focal length
5
c
m
are kept along the same axis with the distance
d
between them. If a prallel beam of light falling on
A
leaves
B
as a parallel beam, then the distance
d
in cm will be
Medium
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>
An object is kept in front of a concave mirror of focal length 20 cm. The image is three times the size of the object.Calculate two possible distance of the object from the mirror.
Medium
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Double convex lenses are to be manufactured from a glass of refractive index 1.55, with both faces of same radius of curvature. What is the radius of curvature required if the focal length is to be 20 cm?
Medium
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>
Derive the following expression for the refraction at concave spherical surface:
v
μ
−
u
1
=
R
μ
−
1
.
Medium
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>
A ray of light falls on a transparent sphere with centre at
C
is shown in Fig.
The ray emerges from the sphere parallel to line
A
B
. The refractive index of the sphere is
Hard
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>
A conversing lens has a focal length of
2
0
c
m
in air. It is made of a material of refractive index
1
.
6
. If it is immersed in a liquid of refractive index
1
.
3
, find the new focal length.
Hard
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>
The focal length of a convex lens of glass
(
μ
=
1
.
5
)
is
2
c
m
. The focal length of the lens when immersed in a liquid of refractive index
1
.
2
5
will be :
Medium
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>
A screen is placed 90 cm away from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 20 cm. Find the focal length of lens.
Medium
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>