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When an object is placed 40cm from a div...

When an object is placed 40cm from a diverging lens, its virtual image is formed 20cm from the lens. The focal length and power of lens are

A

`25 cm`

B

`10 cm`

C

`20 cm`

D

`40 cm`

Text Solution

Verified by Experts

The correct Answer is:
C
Using `1/v-1/u=1/f`, we get
`1/(+(f+40))-1/(-(f+10))=1/(+f)`
Solving this equation, we get
`f=+20 cm`
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