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When an object is at distances x and y f...

When an object is at distances x and y from a lens, a real image and a virtual image is formed respectively having same magnification. The focal length of the lens is

A

`(x+y)/2`

B

x-y

C

`sqrt(xy)`

D

x+y

Text Solution

Verified by Experts

The correct Answer is:
A
(a) For real image,
u=-x
v=+mx
`1/(mx)-1/(-x)=1/f`
For virtual image,
u=-y
Then, v=-my
`1/(-my)-1/(-y)=1/f`
On solving Eqs. (i) and (ii) we get
`f=(x+y)/2`
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