an object placed at its distance from a convex lens of focal length of 24 cm such that the size of the image is one fourth of the object the distances.
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an object placed at its distance from a convex lens of focal length of 24 cm such that the size of the image is one fourth of the object the distances.
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Givenn u=40 cm (negative)
m
=
1
4
(negative for the real image)
a. From
m
=
−
v
u
,
−
1
4
=
−
v
(
−
40
)
or v=-10 cm
Thus the image is formed at a distance 10 cm in front of the mirror.
b. Now from relation
1
u
+
1
v
=
1
f
1
f
=
1
(
−
40
)
+
1
(
−
10
)
=
−
5
40
or
f
=
−
40
5
=
−
8
c
m
i.e., the focal length of concave mirror is 8cm.