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JEE Main Physics Class 12 Ray Optics and Optical Instruments Part 2 Questions
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© examsnet.com
Question : 103
Total: 112
An object is placed at the focus of concave lens having focal length f. What is the magnification and distance of the image from the optical centre of the lens?
[31 Aug 2021 Shift 1]
1
,
∞
Very high, ∞
1
2
,
f
2
1
4
,
f
4
Validate
Solution:
Given, focal length of concave lens, f' = -f
Object distance from lens, u = -f
Image distance from lens = v
Magnification = m
By using lens formula,
1
f
′
=
1
v
−
1
u
⇒
1
v
=
1
f
′
+
1
u
=
−
1
f
−
1
f
=
−
2
f
⇒
v
=
−
f
2
∴
|
v
|
=
f
2
∴
m
=
v
u
=
−
f
2
−
f
=
1
2
© examsnet.com
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