A 2.0 cm tall object is placed perpendicular to the principal axis of convex lens of focal length 10 cm, then
the nature of the image is
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Answer:
12th
Physics
Ray Optics and Optical Instruments
Image Formation by Lenses
A 2.0 cm tall object is pla...
PHYSICS
A 2.0 cm tall object is placed perpendicular to the principal axis of a concave lens of focal length 15 cm. At what distance from the lens, should the object be placed so that it forms an image 10 cm from the lens? Also, find the nature and the size of the image formed.
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ANSWER
According to the question:
Image distance, v=−10 cm
Focal length, f=−15 cm (since, concave lens)
Let the object distance be u.
By lens formula:
v
1
−
u
1
=
f
1
[4pt]
⇒
−10 cm
1
−
u
1
=
−15 cm
1
[4pt]
⇒
u
1
=−
−15 cm
1
−
10 cm
1
[4pt]
⇒
u
1
=
30 cm
2−3
=
30 cm
−1
[4pt]
⇒
u
1
=
30 cm
−1
∴u=−30 cm.
Thus, object should be placed at 30 cm in front of lens, in the same side as image.
Now,
Height of object, h
1
=2 cm
Magnification, m=
h
1
h
2
=
u
v
Putting value of v and u:
Magnification, m=
2 cm
h
2
=
−30 cm
−10 cm
⇒
2 cm
h
2
=
3
1
⇒h
2
=
3
2
cm=0.67 cm
Height of image is 0.67 cm
Thus, the image is virtual, diminished, and erect and one-third the size of object.
Explanation:
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