An object is placed first at infinity an...

An object is placed first at infinity and then at 20 cm from the object side focal plane of a convex lens. The two images thus formed are 5 cm apart the focal length of the lens is

5 cm

10 cm

15 cm

20 cm

Text Solution

Verified by Experts

The correct Answer is:

`u_(1)=oo,v_(1)=f,mu_(2)=f+20,v_(2)=?`
`v_(2)-v_(1),1/f=1/v - 1/u`

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