A 10 mm long awl pin is placed vertically in front pin is formed at 30 cm in front of the mirror the focal length is
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A 10 mm long awl pin is placed vertically in front pin is formed at 30 cm in front of the mirror the focal length is
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Answer:
It is given that the image is formed 30cm in front the mirror.
∴v=−30cm
Also magnification, m=
object height
image height
⇒m=
10mm
5mm
=
2
1
Again, m=
u
v
∴
u
−30
=
2
1
⇒u=−60cm
The mirror formula is given as,
f
1
=
v
1
+
u
1
⇒
f
1
=
−30
1
+
−60
1
⇒
f
1
=
60
−2−1
=−
60
3
=−
20
1
f=−20cm