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Calculate focal length of given lens if ...

Calculate focal length of given lens if the magnification is `-0.5`.

A

`6.66 cm`

B

`5.44 cm`

C

`3.88 cm`

D

`1.38 cm`

Text Solution

Verified by Experts

The correct Answer is:
A
Magnification for lens `= (f)/(u+f) rArr - (1)/(2) = f/(-20+ f)`
`- 20+f= -2f`
`-20 = - 3f`
`f =20//3`
`= 6.66cm`
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