Question

A magnified, inverted image is located at a distance of 40.0 cm from a bi-convex lens with a focal length of 12.0 cm. The object distance is

17.2 cm
15.9 cm
10.5 cm
9.23 cm
7.05 cm

Answer 1

17.2 cm

Step-by-step explanation:

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Answer 2

The object distance is 17.2 cm

As we know, the lens formula is
`(1)/(f)` =
`(1)/(v)` +
`(1)/(u)`

where v = image distance from the lens
u = object distance from the lens
f = focal length of the lens
Alos, focal length of convex lens is positive.

⇒
`(1)/(12)` =
`(1)/(40)` +
`(1)/(u)`

⇒
`(1)/(u)` =
`(1)/(12)` -
`(1)/(40)`

⇒
`(1)/(u)` =
`(10-3)/(120)`

⇒
`(1)/(u)` =
`(7)/(120)`

⇒ u =
`(120)/(7)` = 17.2 cm